title: MFMailComposeViewController View flickering issue
body: <p>When i display the MFMailComposeViewController it view flicker (first goes inside Navigation bar and then come down to correct position) first seems like "To" field goes inside navigation bar and then come out. I am using the following code.`<br>
          self.resignFirstResponder()
          self.mailPicker = MFMailComposeViewController()</p>
  
  <pre><code>    self.mailPicker!.setToRecipients(self.mailer)
      self.mailPicker!.setSubject("hello");
      self.mailPicker!.setMessageBody("message text", isHTML: false);
      self.mailPicker!.mailComposeDelegate = self;
      self.mailPicker!.delegate = self
  
      self.presentViewController(self.mailPicker!, animated: true, completion: nil)`
  </code></pre>