Fixed unit test bug on Windows

- The python-forked module doesn't work on Windows

Author: tleonhardt

CONTRIBUTING.md

@@ -270,8 +270,8 @@ py.test -n4
 ```
 where `4` should be replaced by the number of parallel threads you wish to run for testing.
 
-If you have the `pytest-forked` pytest plugin for running tests in isolated formed processes, you
-can speed things up even further:
+If you have the `pytest-forked` pytest plugin (not avilable on Windows) for running tests in isolated formed processes, 
+you can speed things up even further:
 
 ```shell
 py.test -nauto --forked

setup.py

@@ -77,7 +77,7 @@
     INSTALL_REQUIRES += ['subprocess32']
 
 # unittest.mock was added in Python 3.3.  mock is a backport of unittest.mock to all versions of Python
-TESTS_REQUIRE = ['mock', 'pytest', 'pytest-xdist', 'pytest-forked']
+TESTS_REQUIRE = ['mock', 'pytest', 'pytest-xdist']
 DOCS_REQUIRE = ['sphinx', 'sphinx_rtd_theme', 'pyparsing', 'pyperclip', 'six']
 
 setup(

tox.ini

@@ -34,12 +34,11 @@ deps =
   pyreadline
   pytest
   pytest-cov
-  pytest-forked
   pytest-xdist
   six
   subprocess32
 commands =
-  py.test {posargs: -n 2} --cov=cmd2 --cov-report=term-missing --forked
+  py.test {posargs: -n 2} --cov=cmd2 --cov-report=term-missing
   codecov
 
 [testenv:py34]
@@ -71,10 +70,9 @@ deps =
   pyperclip
   pyreadline
   pytest
-  pytest-forked
   pytest-xdist
   six
-commands = py.test -v -n2 --forked
+commands = py.test -v -n2
 
 [testenv:py36]
 deps =
@@ -98,10 +96,9 @@ deps =
   pyperclip
   pyreadline
   pytest
-  pytest-forked
   pytest-xdist
   six
-commands = py.test -v -n2 --forked
+commands = py.test -v -n2
 
 [testenv:py37]
 deps =