title: UIView Flip Animation Issue
body: <p>I've adopted a fairly well used method of flipping between two images. However on this occasion, for reasons currently beyond me - the animation is currently only flipping from "newView" to "newView."</p>
  
  <p>Any help pointing towards the error of my ways would be greatly appreciated. Code as follows:</p>
  
  <pre><code>UIImageView *oldView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"dark_wood.png"]];
  UIImageView *newView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"light_wood.png"]];
  [container addSubview:oldView];
  </code></pre>
  
  <p>and:</p>
  
  <pre><code>[UIView transitionWithView:container
                    duration:2
                     options:UIViewAnimationOptionTransitionFlipFromLeft
                  animations:^{ [oldView removeFromSuperview]; [container addSubview:newView]; }
                  completion:nil];
  </code></pre>
  
  <p>(It's probably something v.simple beyond this code..)</p>