title: SKCropNode not working properly in Xcode 7 + Swift 2
body: <p>In my SpriteKit game, I have a scrollable node which has a crop node, so it is not visible in the whole screen. I made a node with black color and a very small alpha value and it worked than I expected.</p>
  
  <pre><code>    let rectNode = SKSpriteNode(color: UIColor(red: 0, green: 0, blue: 0, alpha: 0.000001), size: CGSize(width: width, height: height - 100) )
      rectNode.position = CGPoint(x: 0, y: 0)
      rectNode.zPosition = 1
      rectNode.anchorPoint =  CGPoint(x: 0, y: 0)                
  
      rectNode.addChild(contentNode)        
  
      let cropNode = SKCropNode()
      cropNode.maskNode = rectNode.copy() as! SKSpriteNode
      cropNode.addChild(rectNode)
      cropNode.zPosition = 9
  
      addChild(cropNode)
  </code></pre>
  
  <p>Since XCode 7 my content node is not visible, if I change rectNode's alpha to 1, the content is visible with black background, so I think something happened with masking.</p>
  
  <p>Am I doing something wrong or is it a bug in Xcode 7?</p>