Notify test fails with our new changes.

After diving in  I see that because voteable's get_change_observes is overwirting Starrables.

Solution was to also have stars' mixin inherit from ChangeObservable.

However I'm unsure if this will have unwanted changes with meetings or any other starrable model.

One possible thing to do is make another model ChangeObserableStarrable, but I'm not sure if that's the way to or or not. After looking at notify, it's unclear when exactly a notification is sent or not, baced on the mixin.