Summary: We already allow you to create comments, but we don't show them on the
commit page. After style / view unification this is easy; show comments on the
commit page.
Test Plan: Made comments on a commit using the audit too, saw them show up in
Diffusion.
Reviewers: btrahan, jungejason
Reviewed By: btrahan
CC: aran, epriestley
Maniphest Tasks: T904
Differential Revision: https://secure.phabricator.com/D1687
