R1:c52d66e5ba45

Display dependent revisions in revision detail

Summary:
I have a chain of revisions sometimes.
I want to see also revisions depending on me.

Test Plan: Displayed revision in the middle of chain.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D3399