title: Pop over doesn't point over the button
body: <p>I have an application that is compatible with both iPhone and iPad layouts. For iPhone layout I have created Action Sheet and Pop over for iPad. The problem is pop over's arrow does not point over the button I clicked. Below is my code....</p>
  
  <pre><code>let actionSheet = UIAlertController(title: "Choose an option",
              message: "Message",
              preferredStyle: .ActionSheet)
  ...
  
  if UIDevice.currentDevice().userInterfaceIdiom == UIUserInterfaceIdiom.Pad
  {
       // for iPad
       actionSheet.popoverPresentationController?.sourceView = self.view
       actionSheet.popoverPresentationController?.sourceRect = self.view.bounds;
       actionSheet.popoverPresentationController?.permittedArrowDirections = UIPopoverArrowDirection.allZeros;
  }
  
  self.presentViewController(actionSheet, animated: true, completion: nil)
  </code></pre>