更改pushViewController和popViewController的动画效果

from：http://hi.baidu.com/sonnywh/blog/item/6d89b68b8c6234649f2fb43c.html

- (void)pushAnimationDidStop {

}

- (void)pushViewController: (UIViewController*)controller
    animatedWithTransition: (UIViewAnimationTransition)transition {
  [self pushViewController:controller animated:NO];

  [UIView beginAnimations:nil context:nil];
  [UIView setAnimationDuration:TT_FLIP_TRANSITION_DURATION];
  [UIView setAnimationDelegate:self];
  [UIView setAnimationDidStopSelector:@selector(pushAnimationDidStop)];
  [UIView setAnimationTransition:transition forView:self.view cache:YES];
  [UIView commitAnimations];
}

- (UIViewController*)popViewControllerAnimatedWithTransition:(UIViewAnimationTransition)transition {
  UIViewController* poppedController = [self popViewControllerAnimated:NO];

  [UIView beginAnimations:nil context:NULL];
  [UIView setAnimationDuration:TT_FLIP_TRANSITION_DURATION];
  [UIView setAnimationDelegate:self];
  [UIView setAnimationDidStopSelector:@selector(pushAnimationDidStop)];
  [UIView setAnimationTransition:transition forView:self.view cache:NO];
  [UIView commitAnimations];

  return poppedController;
}