title: Drop annotation pins with animation swift2.0
body: <p>I want to drop annotation pins on a mapView with animation. I have tried with below code but it is not working.</p>
  
  <pre><code>anView = MKAnnotationView(annotation: annotation, reuseIdentifier: reuseId)
              anView!.canShowCallout = true
              anView!.animatesDrop = true
  </code></pre>