Use a custom icon to create asset_path urls to icons

Solves the temporary leaflet/rails asset icon path fiasco of
2016 / 2017

app/assets/javascripts/blacklight_heatmaps/default.js

@@ -4,4 +4,5 @@
 //= require leaflet_solr_heatmap
 //= require blacklight_heatmaps/blacklight_heatmaps
 //= require blacklight_heatmaps/basemaps
+//= require blacklight_heatmaps/icons
 //= require_tree ./viewers

app/assets/javascripts/blacklight_heatmaps/icons.js.erb

@@ -0,0 +1,7 @@
+BlacklightHeatmaps.Icons = {
+  default: new L.Icon({
+    iconUrl: '<%= asset_path 'marker-icon.png'%>',
+    iconRetinaUrl: '<%= asset_path 'marker-icon-2x.png'%>',
+    shadowUrl: '<%= asset_path 'marker-shadow.png'%>'
+  })
+};

app/assets/javascripts/blacklight_heatmaps/viewers/show.js

@@ -21,7 +21,13 @@ Blacklight.onLoad(function () {
         $el.data().basemapProvider
       ).addTo(map);
 
-      var features = L.geoJson(features).addTo(map);
+      var features = L.geoJson(features, {
+        pointToLayer: function(feature, latlng) {
+          return L.marker(latlng, {
+            icon: BlacklightHeatmaps.Icons.default
+          })
+        }
+      }).addTo(map);
 
       map.fitBounds(features.getBounds());
     },