Added commit information to 'getrevision' conduit call.

Summary:
differential.getrevision now returns commits for a given revision.
URI is also return in differential.getrevision.

Test Plan:
Tested from Conduit Console UI that the calls were working
correctly.

Reviewed By: jungejason
Reviewers: jungejason
CC: epriestley, simpkins, dpepper, jungejason
Differential Revision: 163