title: Customize MGLPolyline using mapbox
body: <p>Just started using Mapbox, managed to draw a MGLPolyline by adding this in the locationManaged didUpdateLocations </p>
  
  <pre><code>   var shape = MGLPolyline(coordinates: &amp;a, count: UInt(a.count))
     mapView.addAnnotation(shape) 
  </code></pre>
  
  <ol>
  <li>Changing the line width doesn't change it on the screen </li>
  </ol>
  
  <p><code>func mapView(mapView: MGLMapView, lineWidthForPolylineAnnotation annotation: MGLPolyline) -&gt; CGFloat { return 20.0 }</code></p>
  
  <ol start="2">
  <li>How do I change the stroke default color from black to something else? </li>
  </ol>