Make pushes to growth- branches notify the growth hipchat room

Test Plan:
I looked at http://phabricator.khanacademy.org/D13642 and http://phabricator.khanacademy.org/D13391 and the standard practice seems to be yolo?

Would you please help me deploy this through whichever magic flows in this universe?

Reviewers: alpert

Differential Revision: http://phabricator.khanacademy.org/D14484