Bug 1046236 — Log call state modification with the websocket.

https://bugzilla.mozilla.org/show_bug.cgi?id=1046236
Based on #185.
Unfortunately we don't have them now at this point.
We can only know if it is the callee or caller and have their websocketToken but not their uid.

Here we already have the callerId: https://github.com/mozilla-services/loop-server/blob/master/loop/routes/calls.js#L46-L65
We could figure out how to add the calleeId as well so we could query it to write down the log.