title: Touchable image as annotation callout?
body: <p>I tried to use BarButton but this is wrong:</p>
  
  <pre><code>CGSize thumbSize = CGSizeMake(30.0, 30.0);
  UIImageView *annotationThumbnail = [[UIImageView alloc] initWithImage:[((Sight *)annotation).thumbnail imageToFitSize:thumbSize method:MGImageResizeScale]];
  UIBarButtonItem *annotationButton = [[UIBarButtonItem alloc] initWithCustomView:annotationThumbnail];
  
  annotationView.leftCalloutAccessoryView = annotationButton;
  </code></pre>