Make "chat" link title editable on preroll bumper

When chatroom is not in use for slide deck, an editable heading is useful for alternate subtitle, opening comment, etc.

![screen shot 2013-11-08 at 10 23 44 am](https://f.cloud.github.com/assets/352082/1499670/176a812e-4860-11e3-8925-99aa0c90c4fb.png)