Preliminary tests for $firebaseAuth

I took a stab at it. Let me know what you think.
Just *intellectualizing* here: I've started to prefer setting `this.$timeout` vs a global `var $timeout` and the `_$timeout_` notation. Since we're in a beforeEach, `this.$timeout` is available in every scope and doesn't interfere with any other global variables set in the scope chain (a problem I've run into a few times in test units with commonly named variables, not specifically with `$` services from angular).

I haven't made this suggestion for AngularFire specifically and we may keep the current convention for convenience; again, just intellectualizing about the cooking apparatus.