Upgrade MB GL JS to v0.28.0 (close #88)

public/templates/data.tmpl

@@ -37,7 +37,7 @@
     container: 'map',
     hash: true
   });
-  map.addControl(new mapboxgl.Navigation());
+  map.addControl(new mapboxgl.NavigationControl());
 
   function generateColor(str) {
     var rgb = [0, 0, 0];

public/templates/viewer.tmpl

@@ -29,7 +29,7 @@
         style: '/styles/{{id}}.json{{&key_query}}',
         hash: true
       });
-      map.addControl(new mapboxgl.Navigation());
+      map.addControl(new mapboxgl.NavigationControl());
     } else {
       var map = L.mapbox.map('map', '/styles/{{id}}/rendered.json{{&key_query}}', { zoomControl: false });
       new L.Control.Zoom({ position: 'topright' }).addTo(map);