code: function(obj) {
              var arr = this.map.get(obj.x, obj.y);
              var index = arr.indexOf(obj);
              arr.splice(index, 1);
              index = this.objects.indexOf(obj);
              this.objects.splice(index, 1);
              if(obj.onRemove){
                  obj.onRemove();
              }
          }
docs: Removes an entity from the manager.
  @method remove
  @param {Obj} obj - The objity to be removed.