Merge branch 'develop' into message-type-api

* develop:
  Fixed conflicts
  added Git Flow and HISTORY.md
  Deletes direct message subscription for users conversing with user being deleted.
  Fix Room model's removeByTypeContainingUsername.  usernames field missing trailing 's'
  Remove the added console log
  Combine the first two checks into one to make it more readable
  Update message pinning to show up on the tab list with a few options to allow/disallow it and whether to allow anyone to pin messages
  Moved oembed code to a template helper.

Conflicts:
	client/views/app/message.coffee