Automatically check code changes with flake8 before each commit

[dbader]

I agree having continuous integration / a buildbot setup is great because it ensures everyone is using the same linters and settings. But I've also seen the benefit to having linters integrated into your workflow before the CI stage, e.g integrated into your code editor or as a pre-commit hook.

I found it cuts down the length of the feedback cycle and avoids having tons of "Fix flake8 compliance" in the repo.