code: function(x, y, filter) {
              if(filter){
                  var result = this.map.get(x, y);
                  if(result){
                      return result.filter(filter);
                  }
              }
              return this.map.get(x, y);
          }
docs: Retrieves all objects at given map tile coord.
  @method get
  @param {Number} x - The tile map x coord.
  @param {Number} y - The tile map y coord.
  @param {Function} [filter] - A function to filter the array of objects returned `function(object){  return true }`.
  @return {Array}