Improve Diffusion blame views
Summary:
- Make some effort to simplify the code.
- Make "Skip Past This Commit" work in Git and Mercurial.
- Make blame work in Mercurial.
- Add tooltip hover state to show more information about commits.
Test Plan: Viewed blame views in SVN, Git, Hg. Clicked line numbers, hovered/clicked commits, hovered/clicked "blame past..."
Reviewers: btrahan, vrana, jungejason
Reviewed By: vrana
CC: aran
Maniphest Tasks: T378
Differential Revision: https://secure.phabricator.com/D2142