forked from wboykinm's block: Leaflet Omnivore w/ Custom Marker
https://api.tiles.mapbox.com/mapbox.js/v1.6.1/mapbox.js
https://api.tiles.mapbox.com/mapbox.js/plugins/leaflet-omnivore/v0.0.1/leaflet-omnivore.min.js
https://api.tiles.mapbox.com/mapbox.js/plugins/leaflet-markercluster/v0.4.0/leaflet.markercluster.js