Bug 1109569 - Add sound notifications to the room paradigm in FxOS Hello

See bug https://bugzilla.mozilla.org/show_bug.cgi?id=1109569 please. Action happens at https://github.com/jaoo/firefoxos-loop-client/tree/1109569.
If the timeout ends, you must clear the listener as https://github.com/mozilla-b2g/firefoxos-loop-client/pull/384/files#diff-66db6243091dfbc7082f9b300bf20092R148