Bug 971552 - [System2] Instantiable SleepMenu

https://bugzilla.mozilla.org/show_bug.cgi?id=971552

![screen shot 2014-05-22 at 9 05 03 pm](https://cloud.githubusercontent.com/assets/122602/3057956/a42d35ce-e1db-11e3-8896-d7d8a215c36e.png)