title: add circular overlay to mapview
body: <p>I am trying to add a circular overlay in ios mapview,in view did load i added following code</p>
  
  <pre><code>CLLocationCoordinate2D center = CLLocationCoordinate2DMake( 53.809638, -1.554586 );
      MKCircle *circle = [MKCircle circleWithCenterCoordinate:center radius:1000];
      circle.title = @"University of Leeds";
      [self.map addOverlay:circle];
  </code></pre>
  
  <p>and also included the delegate function</p>
  
  <pre><code>- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id &lt;MKOverlay&gt;)overlay {
      if ([overlay isKindOfClass:[MKCircle class]]) {
          MKCircleView *circleView = [[MKCircleView alloc] initWithCircle:(MKCircle*)overlay];
          circleView.fillColor = [[UIColor redColor] colorWithAlphaComponent:0.2];
          circleView.strokeColor = [[UIColor redColor] colorWithAlphaComponent:0.7];
          circleView.lineWidth = 2;
          return circleView;
      }
  </code></pre>
  
  <p>but it's not working why?
  thanks</p>