Bug 1113122 - Notify when I am in a Room and I enter in background mode

See bug https://bugzilla.mozilla.org/show_bug.cgi?id=1113122 please. Action happens at https://github.com/jaoo/firefoxos-loop-client/tree/1113122.
maybe 
```js
_('tapToReturn', {
  roomName: params.roomName
});
```