code: function () {
  
          if (lastLayer) {
              map.removeLayer(lastLayer);
          }
  
          $.ajax({
              //url: 'http://earthquake.usgs.gov/earthquakes/feed/geojsonp/all/day',
              url: 'http://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/all_day.geojsonp',
              type: 'GET',
              dataType: 'jsonp',
              jsonp: false
          });
      }
docs: Function for requesting the latest earthquakes from USGS