Rewrite into Swift of https://www.mapbox.com/mapbox-ios-sdk/examples/marker-image-color/

ViewController.swift

// https://www.mapbox.com/mapbox-ios-sdk/examples/marker-image-color/

import UIKit

//class ViewController: UIViewController
class ViewController: UIViewController, RMMapViewDelegate
{
    
    override func viewDidLoad()
    {
        //[super viewDidLoad];
        super.viewDidLoad()
        
        //[[RMConfiguration configuration] setAccessToken:@"<access token>"];
        
        //RMMapboxSource *tileSource = [[RMMapboxSource alloc] initWithMapID:@"examples.map-z2effxa8"];
        var tileSource: RMMapboxSource = RMMapboxSource(mapID: "examples.map-z2effxa8")
        
        //RMMapView *mapView = [[RMMapView alloc] initWithFrame:self.view.bounds andTilesource:tileSource];
        var mapView: RMMapView = RMMapView(frame: view.bounds, andTilesource: tileSource)
        
        //mapView.delegate = self;
        mapView.delegate = self
        
        //[self.view addSubview:mapView];
        self.view.addSubview(mapView)
        
        //RMAnnotation *annotation = [[RMAnnotation alloc] initWithMapView:mapView coordinate:mapView.centerCoordinate andTitle:@"Bus Stop"];
        var annotation: RMPointAnnotation = RMPointAnnotation(mapView: mapView, coordinate: mapView.centerCoordinate, andTitle: "Bus Stop")
        
        //[mapView addAnnotation:annotation];
        mapView.addAnnotation(annotation)
        
    }
    
    func mapView(mapView: RMMapView!, layerForAnnotation annotation: RMAnnotation!) -> RMMapLayer!
    {
        if (annotation.isUserLocationAnnotation)
        {
            return nil
        }

        var marker: RMMarker = RMMarker(mapboxMarkerImage: "bus", tintColor: UIColor.brownColor())
        marker.canShowCallout = true;
        
        return marker
    }
    
}

it is not working.
should be
var annotation: RMAnnotation = RMAnnotation(mapView: mapView, coordinate: mapView.centerCoordinate, andTitle: "Bus Stop")
so layerForAnnotation delegate method will be successfully invoked and marker will be customized