title: Can not trigger the event of collectionview when add tapGestureRecognizer to its backgroundview
body: <ol>
  <li><p>Add a collectionview into a view Add the view into a</p></li>
  <li><p>backgroundview(UIView) </p></li>
  <li>Add tapGestureRecognizer to the backgroundView</li>
  </ol>
  
  <p>The select event of collectionview can not be triggered when tap a cell,It always trigger the tap event of backgroundview</p>
  
  <pre><code>let backgroundView = UIView(frame: sender.window!.bounds)
      backgroundView.backgroundColor = UIColor.yellowColor()
  
      let blueView = BlueView(frame: CGRect(x: 300, y: 200, width: 300, height: 400))
      backgroundView.addSubview(blueView)
      sender.window!.addSubview(backgroundView)
      backgroundView.userInteractionEnabled = true
  
      let gesture = UITapGestureRecognizer(target: blueView, action: "tapGestureRecognizer")
      gesture.delegate = blueView
      backgroundView.addGestureRecognizer(gesture)
  </code></pre>
  
  <p>..........</p>
  
  <pre><code>    let cv = UICollectionView(frame: CGRect(x: 100, y: 0, width: 100, height: 340), collectionViewLayout: layout)
      cv.registerClass(UICollectionViewCell.self, forCellWithReuseIdentifier: "cell")
      cv.dataSource = self
  
      blueView.addSubview(cv)
  </code></pre>
  
  <p>Who know the reason?</p>