title: UIImage doesn't fade in/out when blur is on
body: <p>I have <code>UIImage</code> which is blurred like this:</p>
  
  <pre><code>myImageView.image = UIImage(named: imageSet[0])
          let blurEffect = UIBlurEffect(style: UIBlurEffectStyle.Light)
          blurEffectView = UIVisualEffectView(effect: blurEffect)
          blurEffectView?.frame = view.bounds
          myImageView.addSubview(blurEffectView!)
  </code></pre>
  
  <p>and then I want to fade in new UIImage like this:</p>
  
  <pre><code>UIView.transitionWithView(self.backgroundImageView,
          duration:1.0,
          options: UIViewAnimationOptions.TransitionCrossDissolve,
          animations: { self.myImageView.image = UIImage(named: self.imageSet[randomInt]
          },
          completion: nil)
  </code></pre>
  
  <p>and the problem is, new image simply appears, rather than fade in. If I disable blur, images fade in and out. What I am doing wrong?</p>