show unread message count when not on chat page

![unread](https://cloud.githubusercontent.com/assets/1459603/5562170/aa30b8aa-8dbc-11e4-97e8-c69717097778.gif)

hopefully adding features out of the blue isn't too frowned upon! i figured this might be nice though, so you can hop in on the excitement of chat when there's stuff going on.