Linting, Support for Django 1.5 user models, Cleanup, etc.

I've updated quite a few things. The biggest changes in the chain come from linting most of the codebase. The tests were linted but some PEP 8 exceptions were made. 

I also refactored the tests to be local to the oauth2 app since they were all oauth2 specific anyways. This was a biproduct of adding support for Django 1.5's configurable user models. Fixture loading for tests would fail if a custom model was defined. Made me realize that there were tests in provider.testcases that were using oauth2 fixture so it became more apparent that things should just be moved down there entirely. 

I also updated the TravisCI config to respond to both master and develop with the idea that feature branches could be merged and built against without affecting master. 

It's a lot, so if you want to break it up in to smaller merges I'll be happy to oblige.

Let me know what you think :)