Remove pep8 naming

So originally we wanted pep8-naming included: https://github.com/markstory/lint-review/pull/24
However, after using it we've realised that it may be too much effort then it's worth. 

Our issue is the same one described here: https://github.com/flintwork/pep8-naming/issues/6 and https://github.com/flintwork/pep8-naming/issues/14

Going around and sticking `# noqa` everywhere is nasty, we could also ignore `N802`, but that requires a change to every repo's `.lintrc`.

I'm sure other users of lint-review would also hit this issue, so instead of forcing them install it we thought that it would be better to give them the choice.