Do a bunch of clean-up work for Review Bot.

Review Request #8423 — Created Sept. 20, 2016 and submitted — Latest diff uploaded

Information

ReviewBot
master
b52d471...

Reviewers

In preparation for some modernization, I'm doing a little bit of clean-up (and
familiarizing myself with the codebase). This change primarily adds
unicode_literals and fixes up docstrings, though there are a few places where
I've made things more idiomatic or simpler.

Verified that the extension loaded correctly. Looked at the various forms in
the admin UI.