Explicitly list which versions of Python 2 and 3 we support

Add logging to our main application

Add methods to report errors to the style guide

A single file works fine now but not a directory

Check for ``# flake8: noqa`` lines inside a file.

Our typical usage always passes is_path_excluded which checks the basename and the full path

pep8's checker has the noqa logic which we've correctly placed on the
StyleGuide object. By passing the StyleGuide in to our checkers we can
have the checkers pass the physical line to the StyleGuide so we can
eliminate our usage of linecache.