title: L.circleMarker on MapBox with options does not work
body: <p>I am trying to add a circle marker to my MapBox but passed options doesn't do what its supposed to do. I am using following code</p>
  
  <pre><code>    L.mapbox.featureLayer(
          { "geometry": {"type": "Point", "coordinates": [lng , lat]}, "type": "Feature", "properties": {} },
          { pointToLayer: function(feature, latlon) { 
              var marker = L.circleMarker(latlon, {
                  radius: 2,
                  color: "#ff0000"
              });
  
              return marker;
          } }
      ).addTo(map);
  </code></pre>
  
  <p>the radius is set but the color is set to default.</p>