Move differential revision to its own table column in blame view

Summary: There is still some layout issues with revisions, so I've tested it better and moved it to it's own column

Test Plan: Fake in some revision data, test various sizes and shapes.

Reviewers: epriestley

Reviewed By: epriestley

Spies: Korvin

Differential Revision: https://secure.phabricator.com/D18473