Users can join a region

https://trello.com/c/W09L9qjM/19-as-a-user-i-can-join-a-region

![screenshot from 2014-11-18 17 11 41](https://cloud.githubusercontent.com/assets/8154429/5097131/005b570c-6f46-11e4-9254-7083c6c4ae20.png)