Convert commits to use unified table of contents

Summary:
Fixes T2183. We now use the same rendering element in both places.

Intentional changes:

• Package highlighting is out, coming back to both apps in next diff.
• removed redundant-feeling "Change" link. The information is now shown with a character ("M", "V", etc.) and the page is a click away under "History". Clicking the path also jumps you to substantially similar content. (We could restore it fairly easily, I just think it's probably the least useful thing in the table right now.)

Test Plan: Viewed a bunch of commits in Diffusion.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T2183

Differential Revision: https://secure.phabricator.com/D13910