R1:51a6ce65aadb

Show blame info in diffusion.

Summary:
Show blame info. This is part of the task of "Port Diffusion's
Browse File view to Phabricator". The color for git repository is not
implemented yet.

Test Plan:
it would work for both git and svn.

Reviewed By: epriestley
Reviewers: epriestley
CC: epriestley
Differential Revision: 87