title: Phone call button in Swift 3 doesn't work
body: <p>I need my app make a phone call when user taps a button. I found some tutorials and people there say use this code</p>
  
  <pre><code>let numberUrl = URL(string: "tel://12345678")!
  UIApplication.shared.open(numberUrl, options: [:], completionHandler: nil)
  </code></pre>
  
  <p>But it just does not work. Was it change in Swift 3?</p>