PyHSPF fails when source directory is greater than 64 chars

[lucashtnguyen]

This issue is similar to #4 but a little nuanced. The package fails when it is installed from source if the source directory is longer than 64 chars. For example, I've installed from my source directory at '/mnt/c/Users/lnguyen/Documents/GitHub/pyHSPF/' but when you add the location of the message wdm file ('src/pyhspf/core/hspfmsg.wdm') we get pasted 64 chars pretty easily.

The message file directory is hard coded into WDMUtil class at line 106.

I propose that the messagepath be an optional kwarg, such as:

class WDMUtil:
    """Class to open and read from WDM files."""

    def __init__(self,
                 verbose = True,
                 messagepath = None,
                 ):
        """
        Initialize WDM environment.

        ...
        self.messagepath = messagepath

        ...
        if not self.messagepath:
            directory = os.path.dirname(hspf.__file__)
            self.messagepath = '{}/pyhspf/core/hspfmsg.wdm'.format(directory)
        """

Which would allow for a user defined location in e.g. './hspfmsg.wdm'
A PR is a click away if this API change is okay by you.

[lucashtnguyen]

Another thought - hspfmsg.wdm could be a package resource file that is copied into a temporary dir during __init__ which would not affect the current API behavior.