R1:8ddfdb26e999

Publish feed stories about commits

Summary: When stuff gets committed, publish feed stories about it.

Test Plan: {F13061}

Reviewers: jungejason, vrana, voldern

Reviewed By: jungejason

CC: aran

Maniphest Tasks: T1322

Differential Revision: https://secure.phabricator.com/D2805