Add hook in travis to notify FB people when they break CI
Add hook in travis to notify FB people when they break CI

Summary:
**what is the change?:**
Add a hook similar to https://github.com/facebook/relay/commit/a1eff1a49aa511426c09c481e942256c751c9281

**why make this change?:**
We want people who sync commits out from FB to be notified (and maybe
stopped?) if their change breaks CI on Github.

**test plan:**
Do it live

**issue:**
Follow up of https://github.com/facebook/draft-js/issues/1364
Closes https://github.com/facebook/draft-js/pull/1373

Differential Revision: D5802523

fbshipit-source-id: 795c29d865c6f0b36a89bb099c7092c9a96d56fd

facebook/draft-js