Add Support for PEP8 Checking

This PR primarily consists of the integration of the pep8 and pep8-naming packages into a new "pep8" tool. I attempted to map the error codes to what your existing strictness profiles seemed to be covering, but since the levels of strictness are subjective, there's obviously room for negotiation.

A bonus addition in this PR is a new output formatter I named "grouped". Instead of being a straight list of error messages, this formatter will group the messages by file and line number, so you can more easily everything that's wrong with a given file or line.

Finally, I also tried to kill off most of the messages that pylint and pep8 were coming up with when run under then veryhigh strictness.