FavoritesTimeline: Just unfavorite the tweet when unfavoriting

Yes, really.
Related to -- and maybe even fixing -- #103
ComposeTweetWindow: Also add all mentioned user when replying

This is the 'normal' behavior. See isseue #97
ComposeTweetWindow: Don't forget the space after the last mention

Forgot that in c434ec29542fb26b779635b8fbf8335a72c52737