title: How to zoom Mapbox using Swift to a given radius in kilometers?
body: <p>I recently updated from legacy Mapbox SDK (version 1.6) to latest Mapbox iOS SDK 3.x.</p>
  
  <p>In new version I am not able to figure out how to zoom Mapbox MGLMapView to a given radius in kilometers to fit on screen.</p>
  
  <p>In old (version 1.6) <code>RMMapView.zoomWithLatitudeLongitudeBoundsSouthWest</code> method does the job as following:</p>
  
  <pre><code>func centerAndZoom(center: CLLocationCoordinate2D, kilometers: Float) {
      let meters = Double(kilometers * 1000)
      let region = MKCoordinateRegionMakeWithDistance(center, meters / 2, meters / 2);
  
      let northEastLat = center.latitude - (region.span.latitudeDelta / 2);
      let northEastLon = center.longitude + (region.span.longitudeDelta / 2);
      let northEast = CLLocationCoordinate2D(latitude: northEastLat, longitude: northEastLon)
  
      let southEastLat = center.latitude + (region.span.latitudeDelta  / 2);
      let southEastLon = center.longitude - (region.span.longitudeDelta / 2);
      let southEast = CLLocationCoordinate2D(latitude: southEastLat, longitude: southEastLon)
  
      self.mapView.zoomWithLatitudeLongitudeBoundsSouthWest(southEast, northEast: northEast, animated: true)
  }
  </code></pre>
  
  <p>How to achieve a radius zoom in latest Mapbox using Swift?</p>