title: window can't addsubview with swift
body: <p>In function Appdelegate - didFinishLaunchingWithOptions implement : </p>
  
  <pre><code>var testView : UIView = UIView(frame: CGRectMake(100, 100, 100, 100))
  testView.backgroundColor = UIColor.blueColor()
  self.window?.addSubview(testView)
  self.window?.bringSubviewToFront(testView)
  self.window?.makeKeyAndVisible()
  </code></pre>
  
  <p>But not show testView.</p>