integrate show/hide method
implement delegate method to setHidden animation
reimplement
- (void)showUIBarsAnimated:(BOOL)animated completion:(void (^)(BOOL finished))completion
- (void)hideUIBarsAnimated:(BOOL)animated completion:(void (^)(BOOL finished))completion
guard unnecessary hide/show call
Merge pull request #1 from takasek/animation-delegate

implement delegate method to setHidden animation