diff --git a/cirpy.py b/cirpy.py
index d417485..cd94287 100644
--- a/cirpy.py
+++ b/cirpy.py
@@ -6,9 +6,9 @@
 https://github.com/mcs07/CIRpy
 """
 
-from __future__ import print_function
-from __future__ import unicode_literals
-from __future__ import division
+
+
+
 import functools
 import inspect
 import logging
@@ -19,8 +19,10 @@
     from urllib.parse import quote, urlencode
     from urllib.request import urlopen
 except ImportError:
-    from urllib import urlencode
-    from urllib2 import quote, urlopen, HTTPError
+    from urllib.parse import urlencode
+    from urllib.parse import quote
+    from urllib.request import urlopen
+    from urllib.error import HTTPError
 
 try:
     from lxml import etree
diff --git a/cirpy.py.bak b/cirpy.py.bak
new file mode 100644
index 0000000..d417485
--- /dev/null
+++ b/cirpy.py.bak
@@ -0,0 +1,448 @@
+# -*- coding: utf-8 -*-
+"""
+CIRpy
+
+Python interface for the Chemical Identifier Resolver (CIR) by the CADD Group at the NCI/NIH.
+https://github.com/mcs07/CIRpy
+"""
+
+from __future__ import print_function
+from __future__ import unicode_literals
+from __future__ import division
+import functools
+import inspect
+import logging
+import os
+
+try:
+    from urllib.error import HTTPError
+    from urllib.parse import quote, urlencode
+    from urllib.request import urlopen
+except ImportError:
+    from urllib import urlencode
+    from urllib2 import quote, urlopen, HTTPError
+
+try:
+    from lxml import etree
+except ImportError:
+    try:
+        import xml.etree.cElementTree as etree
+    except ImportError:
+        import xml.etree.ElementTree as etree
+
+
+__author__ = 'Matt Swain'
+__email__ = 'm.swain@me.com'
+__version__ = '1.0.2'
+__license__ = 'MIT'
+
+log = logging.getLogger('cirpy')
+log.addHandler(logging.NullHandler())
+
+API_BASE = 'https://cactus.nci.nih.gov/chemical/structure'
+FILE_FORMATS = {
+    'alc', 'cdxml', 'cerius', 'charmm', 'cif', 'cml', 'ctx', 'gjf', 'gromacs', 'hyperchem', 'jme', 'maestro', 'mol',
+    'mol2', 'mrv', 'pdb', 'sdf3000', 'sln', 'xyz'
+}
+
+
+def construct_api_url(input, representation, resolvers=None, get3d=False, tautomers=False, xml=True, **kwargs):
+    """Return the URL for the desired API endpoint.
+
+    :param string input: Chemical identifier to resolve
+    :param string representation: Desired output representation
+    :param list(str) resolvers: (Optional) Ordered list of resolvers to use
+    :param bool get3d: (Optional) Whether to return 3D coordinates (where applicable)
+    :param bool tautomers: (Optional) Whether to return all tautomers
+    :param bool xml: (Optional) Whether to return full XML response
+    :returns: CIR API URL
+    :rtype: str
+    """
+    # File formats require representation=file and the format in the querystring
+    if representation in FILE_FORMATS:
+        kwargs['format'] = representation
+        representation = 'file'
+    # Prepend input with 'tautomers:' to return all tautomers
+    if tautomers:
+        input = 'tautomers:%s' % input
+    url = '%s/%s/%s' % (API_BASE, quote(input), representation)
+    if xml:
+        url += '/xml'
+    if resolvers:
+        kwargs['resolver'] = ','.join(resolvers)
+    if get3d:
+        kwargs['get3d'] = True
+    if kwargs:
+        url += '?%s' % urlencode(kwargs)
+    return url
+
+
+def request(input, representation, resolvers=None, get3d=False, tautomers=False, **kwargs):
+    """Make a request to CIR and return the XML response.
+
+    :param string input: Chemical identifier to resolve
+    :param string representation: Desired output representation
+    :param list(string) resolvers: (Optional) Ordered list of resolvers to use
+    :param bool get3d: (Optional) Whether to return 3D coordinates (where applicable)
+    :param bool tautomers: (Optional) Whether to return all tautomers
+    :returns: XML response from CIR
+    :rtype: Element
+    :raises HTTPError: if CIR returns an error code
+    :raises ParseError: if CIR response is uninterpretable
+    """
+    url = construct_api_url(input, representation, resolvers, get3d, tautomers, **kwargs)
+    log.debug('Making request: %s', url)
+    response = urlopen(url)
+    return etree.parse(response).getroot()
+
+
+class Result(object):
+    """A single result returned by CIR."""
+
+    def __init__(self, input, notation, input_format, resolver, representation, value):
+        """
+
+        :param string input: Originally supplied input identifier that produced this result
+        :param string notation: Identifier matched by the resolver or tautomer ID
+        :param string input_format: Format of the input as interpreted by the resolver
+        :param string resolver: Resolver used to produce this result
+        :param string representation: Requested output representation
+        :param value: Actual result value
+        :type value: string or list(string)
+        """
+        self.input = input
+        self.representation = representation
+        self.resolver = resolver
+        self.input_format = input_format
+        self.notation = notation
+        self.value = value
+
+    def __repr__(self):
+        return 'Result(input=%r, representation=%r, resolver=%r, input_format=%r, notation=%r, value=%r)' \
+               % (self.input, self.representation, self.resolver, self.input_format, self.notation, self.value)
+
+    def __str__(self):
+        return self.value
+
+    def __eq__(self, other):
+        return isinstance(other, type(self)) and self.__dict__ == other.__dict__
+
+    def __getitem__(self, prop):
+        """Allow dict-style access to attributes to ease transition from when results were dicts."""
+        if prop in self.__dict__:
+            return getattr(self, prop)
+        raise KeyError(prop)
+
+    def __setitem__(self, prop, val):
+        """Allow dict-style setting of attributes to ease transition from when results were dicts."""
+        setattr(self, prop, val)
+
+    def __contains__(self, prop):
+        """Allow dict-style checking of attributes to ease transition from when results were dicts."""
+        return prop in self.__dict__
+
+    def to_dict(self):
+        """Return a dictionary containing Result data."""
+        return self.__dict__
+
+
+def query(input, representation, resolvers=None, get3d=False, tautomers=False, **kwargs):
+    """Get all results for resolving input to the specified output representation.
+
+    :param string input: Chemical identifier to resolve
+    :param string representation: Desired output representation
+    :param list(string) resolvers: (Optional) Ordered list of resolvers to use
+    :param bool get3d: (Optional) Whether to return 3D coordinates (where applicable)
+    :param bool tautomers: (Optional) Whether to return all tautomers
+    :returns: List of resolved results
+    :rtype: list(Result)
+    :raises HTTPError: if CIR returns an error code
+    :raises ParseError: if CIR response is uninterpretable
+    """
+    tree = request(input, representation, resolvers, get3d, tautomers, **kwargs)
+    results = []
+    for data in tree.findall('.//data'):
+        value = [item.text for item in data.findall('item')]
+        result = Result(
+            input=tree.attrib['string'],
+            representation=tree.attrib['representation'],
+            resolver=data.attrib['resolver'],
+            input_format=data.attrib['string_class'],
+            notation=data.attrib['notation'],
+            value=value[0] if len(value) == 1 else value
+        )
+        results.append(result)
+    log.debug('Received %s query results', len(results))
+    return results
+
+
+def resolve(input, representation, resolvers=None, get3d=False, **kwargs):
+    """Resolve input to the specified output representation.
+
+    :param string input: Chemical identifier to resolve
+    :param string representation: Desired output representation
+    :param list(string) resolvers: (Optional) Ordered list of resolvers to use
+    :param bool get3d: (Optional) Whether to return 3D coordinates (where applicable)
+    :returns: Output representation or None
+    :rtype: string or None
+    :raises HTTPError: if CIR returns an error code
+    :raises ParseError: if CIR response is uninterpretable
+    """
+    # Take first result from XML query
+    results = query(input, representation, resolvers, False, get3d, **kwargs)
+    result = results[0].value if results else None
+    return result
+
+
+def resolve_image(input, resolvers=None, fmt='png', width=300, height=300, frame=False, crop=None, bgcolor=None,
+                  atomcolor=None, hcolor=None, bondcolor=None, framecolor=None, symbolfontsize=11, linewidth=2,
+                  hsymbol='special', csymbol='special', stereolabels=False, stereowedges=True, header=None, footer=None,
+                  **kwargs):
+    """Resolve input to a 2D image depiction.
+
+    :param string input: Chemical identifier to resolve
+    :param list(string) resolvers: (Optional) Ordered list of resolvers to use
+    :param string fmt: (Optional) gif or png image format (default png)
+
+    :param int width: (Optional) Image width in pixels (default 300)
+    :param int height: (Optional) Image height in pixels (default 300)
+    :param bool frame: (Optional) Whether to show border frame (default False)
+    :param int crop: (Optional) Crop image with specified padding
+
+    :param int symbolfontsize: (Optional) Atom label font size (default 11)
+    :param int linewidth: (Optional) Bond line width (default 2)
+
+    :param string bgcolor: (Optional) Background color
+    :param string atomcolor: (Optional) Atom label color
+    :param string hcolor: (Optional) Hydrogen atom label color
+    :param string bondcolor: (Optional) Bond color
+    :param string framecolor: (Optional) Border frame color
+
+    :param bool hsymbol: (Optional) Hydrogens: all, special or none (default special)
+    :param bool csymbol: (Optional) Carbons: all, special or none (default special)
+    :param bool stereolabels: (Optional) Whether to show stereochemistry labels (default False)
+    :param bool stereowedges: (Optional) Whether to show wedge/dash bonds (default True)
+    :param string header: (Optional) Header text above structure
+    :param string footer: (Optional) Footer text below structure
+
+    """
+    # Aggregate all arguments into kwargs
+    args, _, _, values = inspect.getargvalues(inspect.currentframe())
+    for arg in args:
+        if values[arg] is not None:
+            kwargs[arg] = values[arg]
+    # Turn off anti-aliasing for transparent background
+    if kwargs.get('bgcolor') == 'transparent':
+        kwargs['antialiasing'] = False
+    # Renamed parameters
+    if 'stereolabels' in kwargs:
+        kwargs['showstereo'] = kwargs.pop('stereolabels')
+    if 'fmt' in kwargs:
+        kwargs['format'] = kwargs.pop('fmt')
+    # Toggle stereo wedges
+    if 'stereowedges' in kwargs:
+        status = kwargs.pop('stereowedges')
+        kwargs.update({'wedges': status, 'dashes': status})
+    # Constant values
+    kwargs.update({'representation': 'image', 'xml': False})
+    url = construct_api_url(**kwargs)
+    log.debug('Making image request: %s', url)
+    response = urlopen(url)
+    return response.read()
+
+
+# TODO: Support twirl as fmt paramter?
+# TODO: ipython html repr twirl, ipython png repr image
+
+
+
+def download(input, filename, representation, overwrite=False, resolvers=None, get3d=False, **kwargs):
+    """Convenience function to save a CIR response as a file.
+
+    This is just a simple wrapper around the resolve function.
+
+    :param string input: Chemical identifier to resolve
+    :param string filename: File path to save to
+    :param string representation: Desired output representation
+    :param bool overwrite: (Optional) Whether to allow overwriting of an existing file
+    :param list(string) resolvers: (Optional) Ordered list of resolvers to use
+    :param bool get3d: (Optional) Whether to return 3D coordinates (where applicable)
+    :raises HTTPError: if CIR returns an error code
+    :raises ParseError: if CIR response is uninterpretable
+    :raises IOError: if overwrite is False and file already exists
+    """
+    result = resolve(input, representation, resolvers, get3d, **kwargs)
+    # Just log and return if nothing resolved
+    if not result:
+        log.debug('No file to download.')
+        return
+    # Only overwrite an existing file if explicitly instructed to.
+    if not overwrite and os.path.isfile(filename):
+        raise IOError("%s already exists. Use 'overwrite=True' to overwrite it." % filename)
+    # Ensure file ends with a newline
+    if not result.endswith('\n'):
+        result += '\n'
+    with open(filename, 'w') as f:
+        f.write(result)
+
+
+def memoized_property(fget):
+    """Decorator to create memoized properties."""
+    attr_name = '_{0}'.format(fget.__name__)
+    
+    @functools.wraps(fget)
+    def fget_memoized(self):
+        if not hasattr(self, attr_name):
+            setattr(self, attr_name, fget(self))
+        return getattr(self, attr_name)
+    return property(fget_memoized)
+
+
+class Molecule(object):
+    """Class to hold and cache the structure information for a given CIR input."""
+
+    def __init__(self, input, resolvers=None, get3d=False, **kwargs):
+        """Initialize with a resolver input."""
+        self.input = input
+        self.resolvers = resolvers
+        self.get3d = get3d
+        self.kwargs = kwargs
+        log.debug('Instantiated Molecule: %s' % self)
+
+    def __repr__(self):
+        return 'Molecule(input=%r, resolvers=%r, get3d=%r, kwargs=%r)' \
+               % (self.input, self.resolvers, self.get3d, self.kwargs)
+
+    @memoized_property
+    def stdinchi(self):
+        """Standard InChI."""
+        return resolve(self.input, 'stdinchi', self.resolvers, **self.kwargs)
+
+    @memoized_property
+    def stdinchikey(self):
+        """Standard InChIKey."""
+        return resolve(self.input, 'stdinchikey', self.resolvers, **self.kwargs)
+
+    @memoized_property
+    def inchi(self):
+        """Non-standard InChI. (Uses options DONOTADDH W0 FIXEDH RECMET NEWPS SPXYZ SAsXYZ Fb Fnud)."""
+        return resolve(self.input, 'inchi', self.resolvers, **self.kwargs)
+
+    @memoized_property
+    def smiles(self):
+        """SMILES string."""
+        return resolve(self.input, 'smiles', self.resolvers, **self.kwargs)
+
+    @memoized_property
+    def ficts(self):
+        """FICTS NCI/CADD hashed structure identifier."""
+        return resolve(self.input, 'ficts', self.resolvers, **self.kwargs)
+
+    @memoized_property
+    def ficus(self):
+        """FICuS NCI/CADD hashed structure identifier."""
+        return resolve(self.input, 'ficus', self.resolvers, **self.kwargs)
+
+    @memoized_property
+    def uuuuu(self):
+        """uuuuu NCI/CADD hashed structure identifier."""
+        return resolve(self.input, 'uuuuu', self.resolvers, **self.kwargs)
+
+    @memoized_property
+    def hashisy(self):
+        """CACTVS HASHISY identifier."""
+        return resolve(self.input, 'hashisy', self.resolvers, **self.kwargs)
+
+    @memoized_property
+    def sdf(self):
+        """SDF file."""
+        return resolve(self.input, 'sdf', self.resolvers, **self.kwargs)
+
+    @memoized_property
+    def names(self):
+        """List of chemical names."""
+        return resolve(self.input, 'names', self.resolvers, **self.kwargs)
+
+    @memoized_property
+    def iupac_name(self):
+        """IUPAC approved name."""
+        return resolve(self.input, 'iupac_name', self.resolvers, **self.kwargs)
+
+    @memoized_property
+    def cas(self):
+        """CAS registry numbers."""
+        return resolve(self.input, 'cas', self.resolvers, **self.kwargs)
+
+    @memoized_property
+    def mw(self):
+        """Molecular weight."""
+        return resolve(self.input, 'mw', self.resolvers, **self.kwargs)
+
+    @memoized_property
+    def formula(self):
+        """Molecular formula"""
+        return resolve(self.input, 'formula', self.resolvers, **self.kwargs)
+
+    @memoized_property
+    def h_bond_donor_count(self):
+        """Hydrogen bond donor count."""
+        return resolve(self.input, 'h_bond_donor_count', self.resolvers, **self.kwargs)
+
+    @memoized_property
+    def h_bond_acceptor_count(self):
+        """Hydrogen bond acceptor count."""
+        return resolve(self.input, 'h_bond_acceptor_count', self.resolvers, **self.kwargs)
+
+    @memoized_property
+    def h_bond_center_count(self):
+        """Hydrogen bond center count."""
+        return resolve(self.input, 'h_bond_center_count', self.resolvers, **self.kwargs)
+
+    @memoized_property
+    def rule_of_5_violation_count(self):
+        """Rule of 5 violation count."""
+        return resolve(self.input, 'rule_of_5_violation_count', self.resolvers, **self.kwargs)
+
+    @memoized_property
+    def rotor_count(self):
+        """Rotor count."""
+        return resolve(self.input, 'rotor_count', self.resolvers, **self.kwargs)
+
+    @memoized_property
+    def effective_rotor_count(self):
+        """Effective rotor count."""
+        return resolve(self.input, 'effective_rotor_count', self.resolvers, **self.kwargs)
+
+    @memoized_property
+    def ring_count(self):
+        """Ring count."""
+        return resolve(self.input, 'ring_count', self.resolvers, **self.kwargs)
+
+    @memoized_property
+    def ringsys_count(self):
+        """Ring system count."""
+        return resolve(self.input, 'ringsys_count', self.resolvers, **self.kwargs)
+
+    @memoized_property
+    def image(self):
+        """2D image depiction."""
+        return resolve_image(self.input, self.resolvers, **self.kwargs)
+
+    @property
+    def image_url(self):
+        """URL of a GIF image."""
+        return construct_api_url(self.input, 'image', self.resolvers, False, self.get3d, False, **self.kwargs)
+
+    @property
+    def twirl_url(self):
+        """Url of a TwirlyMol 3D viewer."""
+        return construct_api_url(self.input, 'twirl', self.resolvers, False, self.get3d, False, **self.kwargs)
+
+    def download(self, filename, representation, overwrite=False):
+        """Download the resolved structure as a file.
+
+        :param string filename: File path to save to
+        :param string representation: Desired output representation
+        :param bool overwrite: (Optional) Whether to allow overwriting of an existing file
+        """
+        download(self.input, filename, representation, overwrite, self.resolvers, self.get3d, **self.kwargs)
diff --git a/cirpy_test.py b/cirpy_test.py
index eb6b18c..6e14735 100644
--- a/cirpy_test.py
+++ b/cirpy_test.py
@@ -6,9 +6,9 @@
 https://github.com/mcs07/CIRpy
 """
 
-from __future__ import print_function
-from __future__ import unicode_literals
-from __future__ import division
+
+
+
 import logging
 import os
 import time
@@ -17,7 +17,7 @@
 try:
     from urllib.error import HTTPError
 except ImportError:
-    from urllib2 import HTTPError
+    from urllib.error import HTTPError
 
 try:
     from lxml import etree
diff --git a/cirpy_test.py.bak b/cirpy_test.py.bak
new file mode 100644
index 0000000..eb6b18c
--- /dev/null
+++ b/cirpy_test.py.bak
@@ -0,0 +1,190 @@
+# -*- coding: utf-8 -*-
+"""
+Unit tests for cirpy.py
+
+Python interface for the Chemical Identifier Resolver (CIR) by the CADD Group at the NCI/NIH.
+https://github.com/mcs07/CIRpy
+"""
+
+from __future__ import print_function
+from __future__ import unicode_literals
+from __future__ import division
+import logging
+import os
+import time
+import unittest
+
+try:
+    from urllib.error import HTTPError
+except ImportError:
+    from urllib2 import HTTPError
+
+try:
+    from lxml import etree
+except ImportError:
+    try:
+        import xml.etree.cElementTree as etree
+    except ImportError:
+        import xml.etree.ElementTree as etree
+
+from cirpy import request, resolve, query, Molecule, Result, resolve_image
+
+
+logging.basicConfig(level=logging.DEBUG)
+
+
+class RateLimitTestCase(unittest.TestCase):
+    """TestCase that delays before each test according to CIRPY_TEST_DELAY environment variable."""
+
+    def setUp(self):
+        time.sleep(float(os.environ.get('CIRPY_TEST_DELAY', 0)))
+
+
+class TestRequest(RateLimitTestCase):
+    """Test basic requests to CIR servers return the expected XML response."""
+
+    def test_requests(self):
+        """Test a variety of basic requests to ensure they return the expected XML response."""
+        self.assertEqual(request('c1ccccc1', 'names').tag, 'request')
+        self.assertEqual(request('Aspirin', 'smiles').tag, 'request')
+        self.assertEqual(len(request('64-17-5', 'stdinchi')), 1)
+
+    def test_no_result_request(self):
+        """Test that an empty XML response is returned when there are no results."""
+        response = request('arguergbaiurg', 'smiles')
+        self.assertEqual(response.tag, 'request')
+        self.assertEqual(len(response), 0)
+
+    def test_invalid_representation_request(self):
+        """Test that HTTPError is raised when an invalid representation is specified."""
+        with self.assertRaises(HTTPError):
+            request('Morphine', 'ogiuewrgpw')
+
+
+class TestQuery(RateLimitTestCase):
+    """Test the query function returns expected results."""
+
+    def test_morphine_inchi(self):
+        """Test morphine query for inchi returns expected result."""
+        results = query('morphine', 'inchi')
+        self.assertEqual(len(results), 2)
+        self.assertEqual(results[1].input, 'morphine')
+        self.assertEqual(results[1].representation, 'inchi')
+        self.assertEqual(results[1].resolver, 'name_by_cir')
+        self.assertEqual(results[1].input_format, 'chemical name (CIR)')
+        self.assertEqual(results[1].notation, 'Morphine')
+        self.assertEqual(results[1].value, 'InChI=1/C17H19NO3/c1-18-7-6-17-10-3-5-13(20)16(17)21-15-12(19)4-2-9(14(15)17)8-11(10)18/h2-5,10-11,13,16,19-20H,6-8H2,1H3/t10-,11+,13?,16-,17-/m0/s1')
+
+    def test_query_dict(self):
+        """Test dict-style access to result attributes."""
+        results = query('Morphine', 'inchi')
+        self.assertEqual(len(results), 2)
+        self.assertEqual(results[1]['value'], 'InChI=1/C17H19NO3/c1-18-7-6-17-10-3-5-13(20)16(17)21-15-12(19)4-2-9(14(15)17)8-11(10)18/h2-5,10-11,13,16,19-20H,6-8H2,1H3/t10-,11+,13?,16-,17-/m0/s1')
+        self.assertEqual(results[1]['notation'], 'Morphine')
+        self.assertEqual(results[1]['resolver'], 'name_by_cir')
+
+    def test_no_result_query(self):
+        """Test that an empty list is returned when there are no results."""
+        self.assertEqual(query('sjkvhaldfu', 'smiles'), [])
+
+    def test_invalid_representation_query(self):
+        """Test that HTTPError is raised when an invalid representation is specified."""
+        with self.assertRaises(HTTPError):
+            query('Morphine', 'ogiuewrgpw')
+
+    def test_custom_resolvers(self):
+        """Test expected results are returned when using custom name resolvers."""
+        results = query('2,4,6-trinitrotoluene', 'smiles')
+        self.assertEqual(len(results), 2)
+        self.assertEqual(results[0], Result(input='2,4,6-trinitrotoluene', representation='smiles', resolver='name_by_opsin', input_format='IUPAC name (OPSIN)', notation='2,4,6-trinitrotoluene', value='Cc1c(cc(cc1[N+]([O-])=O)[N+]([O-])=O)[N+]([O-])=O'))
+        self.assertEqual(results[1], Result(input='2,4,6-trinitrotoluene', representation='smiles', resolver='name_by_cir', input_format='chemical name (CIR)', notation='2,4,6-Trinitrotoluene', value='Cc1c(cc(cc1[N+]([O-])=O)[N+]([O-])=O)[N+]([O-])=O'))
+
+    def test_result_equality(self):
+        """Test that identical result objects are considered equal."""
+        r1 = Result('input', 'notation', 'input_format', 'resolver', 'representation', 'value')
+        r2 = Result('input', 'notation', 'input_format', 'resolver', 'representation', 'value')
+        r3 = Result('input', 'notation', 'input_format', 'resolver', 'representation', 'another_value')
+        self.assertEqual(r1, r2)
+        self.assertNotEqual(r1, r3)
+
+
+class TestResolve(RateLimitTestCase):
+    """Test the resolve function."""
+
+    def test_alanine_smiles(self):
+        """Test that alanine smiles resolves the expected result."""
+        self.assertEqual(resolve('Alanine', 'smiles'), 'C[C@H](N)C(O)=O')
+
+    def test_no_results_resolve(self):
+        """Test that None is returned when there are no results."""
+        self.assertEqual(resolve('aruighaelirugaerg', 'inchi'), None)
+
+    def test_invalid_representation_resolve(self):
+        """Test that HTTPError is raised when an invalid representation is specified."""
+        with self.assertRaises(HTTPError):
+            resolve('Morphine', 'ogiuewrgpw')
+
+    def test_tnt_smiles(self):
+        """Test that TNT smiles resolves the expected result."""
+        self.assertEqual(
+            resolve('2,4,6-trinitrotoluene', 'smiles'),
+            'Cc1c(cc(cc1[N+]([O-])=O)[N+]([O-])=O)[N+]([O-])=O'
+        )
+
+    def test_tnt_smiles_custom_resolvers(self):
+        """Test custom resolvers return the expected result."""
+        self.assertEqual(
+            resolve('2,4,6-trinitrotoluene', 'smiles', ['name_by_opsin', 'name_by_cir']),
+            'Cc1c(cc(cc1[N+]([O-])=O)[N+]([O-])=O)[N+]([O-])=O'
+        )
+        self.assertEqual(
+            resolve('2,4,6-trinitrotoluene', 'smiles', ['name_by_cir', 'name_by_opsin']),
+            'Cc1c(cc(cc1[N+]([O-])=O)[N+]([O-])=O)[N+]([O-])=O'
+        )
+
+
+class TestMolecule(RateLimitTestCase):
+    """Test the Molecule class."""
+
+    def test_molecule_image(self):
+        """Test Molecule image_url attribute."""
+        self.assertEqual(
+            Molecule('C#N', ['smiles']).image_url,
+            'https://cactus.nci.nih.gov/chemical/structure/C%23N/image?resolver=smiles'
+        )
+
+
+class TestFiles(RateLimitTestCase):
+    """Test resolving to file formats."""
+
+    def test_cml(self):
+        """Test CML file format is resolved."""
+        cmlstring = resolve('Aspirin', 'cml')
+        cml = etree.fromstring(cmlstring)
+        self.assertEqual(cml.tag, '{http://www.xml-cml.org/schema/cml2/core}list')
+        self.assertEqual(len(cml.findall('.//{http://www.xml-cml.org/schema/cml2/core}molecule')), 1)
+
+    def test_pdb(self):
+        """Test PDB file format is resolved."""
+        result = resolve('Aspirin', 'pdb')
+        self.assertIn('HEADER', result)
+        self.assertIn('ATOM', result)
+        self.assertIn('CONECT', result)
+
+
+class TestImage(RateLimitTestCase):
+    """Test resolving to image depiction."""
+
+    def test_png_format(self):
+        """Test that response looks like valid PNG data."""
+        img = resolve_image('Glucose')
+        self.assertEqual(img[:8], b'\x89PNG\x0d\x0a\x1a\x0a')
+
+    def test_gif_format(self):
+        """Test that response looks like valid GIF data."""
+        img = resolve_image('Glucose', fmt='gif')
+        self.assertEqual(img[:4], b'GIF8')
+
+
+if __name__ == '__main__':
+    unittest.main()
diff --git a/docs/source/conf.py b/docs/source/conf.py
index 45ab904..11f66a6 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -39,8 +39,8 @@
 master_doc = 'index'
 
 # General information about the project.
-project = u'CIRpy'
-copyright = u'2015, Matt Swain'
+project = 'CIRpy'
+copyright = '2015, Matt Swain'
 
 # The version info for the project you're documenting, acts as replacement for |version| and |release|, also used in
 # various other places throughout the built documents.
@@ -179,7 +179,7 @@
 # Grouping the document tree into LaTeX files. List of tuples
 # (source start file, target name, title, author, documentclass [howto, manual, or own class]).
 latex_documents = [
-  ('index', 'CIRpy.tex', u'CIRpy Documentation', u'Matt Swain', 'manual'),
+  ('index', 'CIRpy.tex', 'CIRpy Documentation', 'Matt Swain', 'manual'),
 ]
 
 # The name of an image file (relative to this directory) to place at the top of the title page.
@@ -205,7 +205,7 @@
 
 # One entry per manual page. List of tuples (source start file, name, description, authors, manual section).
 man_pages = [
-    ('index', 'cirpy', u'CIRpy Documentation', [u'Matt Swain'], 1)
+    ('index', 'cirpy', 'CIRpy Documentation', ['Matt Swain'], 1)
 ]
 
 # If true, show URL addresses after external links.
@@ -217,7 +217,7 @@
 # Grouping the document tree into Texinfo files. List of tuples
 # (source start file, target name, title, author, dir menu entry, description, category)
 texinfo_documents = [
-    ('index', 'CIRpy', u'CIRpy Documentation', u'Matt Swain', 'CIRpy',
+    ('index', 'CIRpy', 'CIRpy Documentation', 'Matt Swain', 'CIRpy',
      'One line description of project.', 'Miscellaneous'),
 ]
 
@@ -237,10 +237,10 @@
 # -- Options for Epub output ----------------------------------------------
 
 # Bibliographic Dublin Core info.
-epub_title = u'CIRpy'
-epub_author = u'Matt Swain'
-epub_publisher = u'Matt Swain'
-epub_copyright = u'2015, Matt Swain'
+epub_title = 'CIRpy'
+epub_author = 'Matt Swain'
+epub_publisher = 'Matt Swain'
+epub_copyright = '2015, Matt Swain'
 
 # The basename for the epub file. It defaults to the project name.
 #epub_basename = u'CIRpy'
diff --git a/docs/source/conf.py.bak b/docs/source/conf.py.bak
new file mode 100644
index 0000000..45ab904
--- /dev/null
+++ b/docs/source/conf.py.bak
@@ -0,0 +1,312 @@
+# -*- coding: utf-8 -*-
+# CIRpy documentation build configuration file, created by sphinx-quickstart on Tue Mar 24 16:12:38 2015.
+# This file is execfile()d with the current directory set to its containing dir.
+# Note that not all possible configuration values are present in this autogenerated file.
+# All configuration values have a default; values that are commented out serve to show the default.
+
+import sys
+import os
+
+# on_rtd is whether we are on readthedocs.org
+on_rtd = os.environ.get('READTHEDOCS', None) == 'True'
+
+# If extensions (or modules to document with autodoc) are in another directory, add these directories to sys.path here.
+# If the directory is relative to the documentation root, use os.path.abspath to make it absolute, like shown here.
+sys.path.insert(0, os.path.abspath('../..'))
+
+# -- General configuration ------------------------------------------------
+
+# If your documentation needs a minimal Sphinx version, state it here.
+#needs_sphinx = '1.0'
+
+# Add any Sphinx extension module names here, as strings. They can be extensions coming with Sphinx
+# (named 'sphinx.ext.*') or your custom ones.
+extensions = [
+    'sphinx.ext.autodoc',
+    'sphinx.ext.intersphinx',
+]
+
+# Add any paths that contain templates here, relative to this directory.
+templates_path = ['_templates']
+
+# The suffix of source filenames.
+source_suffix = '.rst'
+
+# The encoding of source files.
+#source_encoding = 'utf-8-sig'
+
+# The master toctree document.
+master_doc = 'index'
+
+# General information about the project.
+project = u'CIRpy'
+copyright = u'2015, Matt Swain'
+
+# The version info for the project you're documenting, acts as replacement for |version| and |release|, also used in
+# various other places throughout the built documents.
+#
+# The short X.Y version.
+version = '1.0.2'
+# The full version, including alpha/beta/rc tags.
+release = '1.0.2'
+
+# The language for content autogenerated by Sphinx. Refer to documentation for a list of supported languages.
+#language = None
+
+# There are two options for replacing |today|: either, you set today to some non-false value, then it is used:
+#today = ''
+# Else, today_fmt is used as the format for a strftime call.
+#today_fmt = '%B %d, %Y'
+
+# List of patterns, relative to source directory, that match files and directories to ignore when looking for source
+# files.
+exclude_patterns = []
+
+# The reST default role (used for this markup: `text`) to use for all documents.
+#default_role = None
+
+# If true, '()' will be appended to :func: etc. cross-reference text.
+#add_function_parentheses = True
+
+# If true, the current module name will be prepended to all description unit titles (such as .. function::).
+#add_module_names = True
+
+# If true, sectionauthor and moduleauthor directives will be shown in the output. They are ignored by default.
+#show_authors = False
+
+# The name of the Pygments (syntax highlighting) style to use.
+pygments_style = 'sphinx'
+
+# A list of ignored prefixes for module index sorting.
+#modindex_common_prefix = []
+
+# If true, keep warnings as "system message" paragraphs in the built documents.
+#keep_warnings = False
+
+
+# -- Options for HTML output ----------------------------------------------
+
+# The theme to use for HTML and HTML Help pages.  See the documentation for a list of builtin themes.
+if not on_rtd:  # only import and set the theme if we're building docs locally
+    import sphinx_rtd_theme
+    html_theme = 'sphinx_rtd_theme'
+    html_theme_path = [sphinx_rtd_theme.get_html_theme_path()]
+
+#html_theme = 'default'
+
+# Theme options are theme-specific and customize the look and feel of a theme further. For a list of options available
+# for each theme, see the documentation.
+#html_theme_options = {}
+
+# Add any paths that contain custom themes here, relative to this directory.
+#html_theme_path = []
+
+# The name for this set of Sphinx documents.  If None, it defaults to "<project> v<release> documentation".
+#html_title = None
+
+# A shorter title for the navigation bar.  Default is the same as html_title.
+#html_short_title = None
+
+# The name of an image file (relative to this directory) to place at the top of the sidebar.
+#html_logo = None
+
+# The name of an image file (within the static path) to use as favicon of the docs. This file should be a Windows icon
+# file (.ico) being 16x16 or 32x32 pixels large.
+#html_favicon = None
+
+# Add any paths that contain custom static files (such as style sheets) here, relative to this directory. They are
+# copied after the builtin static files, so a file named "default.css" will overwrite the builtin "default.css".
+html_static_path = ['_static']
+
+# Add any extra paths that contain custom files (such as robots.txt or .htaccess) here, relative to this directory.
+# These files are copied directly to the root of the documentation.
+#html_extra_path = []
+
+# If not '', a 'Last updated on:' timestamp is inserted at every page bottom, using the given strftime format.
+#html_last_updated_fmt = '%b %d, %Y'
+
+# If true, SmartyPants will be used to convert quotes and dashes to typographically correct entities.
+#html_use_smartypants = True
+
+# Custom sidebar templates, maps document names to template names.
+#html_sidebars = {}
+
+# Additional templates that should be rendered to pages, maps page names to template names.
+#html_additional_pages = {}
+
+# If false, no module index is generated.
+#html_domain_indices = True
+
+# If false, no index is generated.
+#html_use_index = True
+
+# If true, the index is split into individual pages for each letter.
+#html_split_index = False
+
+# If true, links to the reST sources are added to the pages.
+#html_show_sourcelink = True
+
+# If true, "Created using Sphinx" is shown in the HTML footer. Default is True.
+#html_show_sphinx = True
+
+# If true, "(C) Copyright ..." is shown in the HTML footer. Default is True.
+#html_show_copyright = True
+
+# If true, an OpenSearch description file will be output, and all pages will contain a <link> tag referring to it. The
+# value of this option must be the base URL from which the finished HTML is served.
+#html_use_opensearch = ''
+
+# This is the file name suffix for HTML files (e.g. ".xhtml").
+#html_file_suffix = None
+
+# Output file base name for HTML help builder.
+htmlhelp_basename = 'CIRpydoc'
+
+
+# -- Options for LaTeX output ---------------------------------------------
+
+latex_elements = {
+# The paper size ('letterpaper' or 'a4paper').
+'papersize': 'a4paper',
+
+# The font size ('10pt', '11pt' or '12pt').
+'pointsize': '12pt',
+
+# Additional stuff for the LaTeX preamble.
+#'preamble': '',
+}
+
+# Grouping the document tree into LaTeX files. List of tuples
+# (source start file, target name, title, author, documentclass [howto, manual, or own class]).
+latex_documents = [
+  ('index', 'CIRpy.tex', u'CIRpy Documentation', u'Matt Swain', 'manual'),
+]
+
+# The name of an image file (relative to this directory) to place at the top of the title page.
+#latex_logo = None
+
+# For "manual" documents, if this is true, then toplevel headings are parts, not chapters.
+latex_use_parts = False
+
+# If true, show page references after internal links.
+latex_show_pagerefs = True
+
+# If true, show URL addresses after external links.
+latex_show_urls = True
+
+# Documents to append as an appendix to all manuals.
+#latex_appendices = []
+
+# If false, no module index is generated.
+latex_domain_indices = False
+
+
+# -- Options for manual page output ---------------------------------------
+
+# One entry per manual page. List of tuples (source start file, name, description, authors, manual section).
+man_pages = [
+    ('index', 'cirpy', u'CIRpy Documentation', [u'Matt Swain'], 1)
+]
+
+# If true, show URL addresses after external links.
+#man_show_urls = False
+
+
+# -- Options for Texinfo output -------------------------------------------
+
+# Grouping the document tree into Texinfo files. List of tuples
+# (source start file, target name, title, author, dir menu entry, description, category)
+texinfo_documents = [
+    ('index', 'CIRpy', u'CIRpy Documentation', u'Matt Swain', 'CIRpy',
+     'One line description of project.', 'Miscellaneous'),
+]
+
+# Documents to append as an appendix to all manuals.
+#texinfo_appendices = []
+
+# If false, no module index is generated.
+#texinfo_domain_indices = True
+
+# How to display URL addresses: 'footnote', 'no', or 'inline'.
+#texinfo_show_urls = 'footnote'
+
+# If true, do not generate a @detailmenu in the "Top" node's menu.
+#texinfo_no_detailmenu = False
+
+
+# -- Options for Epub output ----------------------------------------------
+
+# Bibliographic Dublin Core info.
+epub_title = u'CIRpy'
+epub_author = u'Matt Swain'
+epub_publisher = u'Matt Swain'
+epub_copyright = u'2015, Matt Swain'
+
+# The basename for the epub file. It defaults to the project name.
+#epub_basename = u'CIRpy'
+
+# The HTML theme for the epub output. Since the default themes are not optimized for small screen space, using the same
+# theme for HTML and epub output is usually not wise. This defaults to 'epub', a theme designed to save visual space.
+#epub_theme = 'epub'
+
+# The language of the text. It defaults to the language option
+# or en if the language is not set.
+#epub_language = ''
+
+# The scheme of the identifier. Typical schemes are ISBN or URL.
+#epub_scheme = ''
+
+# The unique identifier of the text. This can be a ISBN number
+# or the project homepage.
+#epub_identifier = ''
+
+# A unique identification for the text.
+#epub_uid = ''
+
+# A tuple containing the cover image and cover page html template filenames.
+#epub_cover = ()
+
+# A sequence of (type, uri, title) tuples for the guide element of content.opf.
+#epub_guide = ()
+
+# HTML files that should be inserted before the pages created by sphinx.
+# The format is a list of tuples containing the path and title.
+#epub_pre_files = []
+
+# HTML files shat should be inserted after the pages created by sphinx.
+# The format is a list of tuples containing the path and title.
+#epub_post_files = []
+
+# A list of files that should not be packed into the epub file.
+epub_exclude_files = ['search.html']
+
+# The depth of the table of contents in toc.ncx.
+#epub_tocdepth = 3
+
+# Allow duplicate toc entries.
+#epub_tocdup = True
+
+# Choose between 'default' and 'includehidden'.
+#epub_tocscope = 'default'
+
+# Fix unsupported image types using the PIL.
+#epub_fix_images = False
+
+# Scale large images.
+#epub_max_image_width = 0
+
+# How to display URL addresses: 'footnote', 'no', or 'inline'.
+#epub_show_urls = 'inline'
+
+# If false, no index is generated.
+#epub_use_index = True
+
+
+# Example configuration for intersphinx: refer to the Python standard library.
+intersphinx_mapping = {'python': ('http://docs.python.org/', None)}
+
+# Sort autodoc members by the order they appear in the source code
+autodoc_member_order = 'bysource'
+
+# Concatenate the class and __init__ docstrings together
+autoclass_content = 'both'