Update pep8 to 1.5.7

This is just to keep us on the upgrade treadmill. ([Changelog](https://pypi.python.org/pypi/pep8#changelog))
@dmitchell: git blame [tagged you as the author of these comments](https://github.com/edx/edx-platform/commit/50296593). If you think they're important, can you explain them in two or three sentences? Right now, I have no idea what the comments mean or why they're important to keep. If you explain them, then I can replace these confusing comments with the clearer comments.

Incidentally, the reason this PR is suggesting that the comments should be deleted is because `pep8` flags them with indentation issues. Yet another reason why they should be rewritten.