title: How do I remove all map annotations in swift 2
body: <p>I had working code to remove all map annotations with a button, but after my update to xcode 7 I am running into the error: </p>
  
  <p>Type 'MKAnnotation' does not conform to protocol 'SequenceType'</p>
  
  <pre><code>if let annotations = (self.mapView.annotations as? MKAnnotation){
      for _annotation in annotations {
          if let annotation = _annotation as? MKAnnotation {
              self.mapView.removeAnnotation(annotation)
          }
      }
  }
  </code></pre>