Apparently flake8 v3 doesn't like trailing comments on config settings.

Also remove the pep8 config, which didn't work (because it was missing W503)
and duplicated the flake8 config. We don't use pep8 on its own, so the config
was duplicative.

pycharm supports them so there is no need to use the other format.

Might as well convert the existing strings to reduce the risk of
people accidentally cargo culting the wrong doc string format.