title: Can't get iOS MapKit Annotation to show title and subtitle
body: <p>I'm having issues showing a map annotation within xCode. I am able to show a pin on the correct coordinates, however I cannot seem to figure out how to show an annotation with a title and subtitle.</p>
  
  <p>I'm a newbie to xCode and Swift, so apologies if I use incorrect terminology (or if this is a really simple problem to solve!) I've been searching the web for about 2 hours now, trying different variations to my code, but I can't get it working!</p>
  
  <p>I'm developing a simple app where users can browse locations and then see it pinned on a map. Once people click through from a location to the MapViewController, I'm trying to just show a map with the location pinned and an annotation with title and subtitle. I've figured everything out except for the title and subtitle, so I'd appreciate any help!</p>
  
  <pre><code>override func viewDidLoad() {
      super.viewDidLoad()
  
      // Location pin
      let initialLocation = CLLocation(latitude: location.latitude, longitude: location.longitude)
      self.centerMapOnLocation(location: initialLocation)
  
  
      // Annotation
      let annotation = MKPointAnnotation()
      annotation.title = self.location.name
      annotation.subtitle = self.location.type
      annotation.coordinate = CLLocationCoordinate2D(latitude: location.latitude, longitude: location.longitude)
      mapView.addAnnotation(location)
  
  }
  
  // Map Center on Location
  func centerMapOnLocation(location: CLLocation) {
      let regionRadius: CLLocationDistance = 1000
      let coordinateRegion = MKCoordinateRegionMakeWithDistance(location.coordinate,
      regionRadius * 2.0, regionRadius * 2.0)
      mapView.setRegion(coordinateRegion, animated: true)
  }
  
  override func didReceiveMemoryWarning() {
      super.didReceiveMemoryWarning()
  }
  </code></pre>