code: function MultiObjectManager(game, ObjectConstructor, width, height) {
          this.game = game;
          this.ObjectConstructor = ObjectConstructor;
          this.objects = [];
          this.map = new RL.Array2d();
          this.setSize(width, height);
  
          var map = this.map;
          this.map.each(function(val, x, y){
              map.set(x, y, []);
          });
      }
docs: Manages a list of object and their tile positions.
  Multiple objects can be at a given tile map coord.
  Handles adding, removing, moving objects within the game.
  @class MultiObjectManager
  @constructor
  @param {Game} game - Game instance this `MultiObjectManager` is attached to.
  @param {Object} ObjectConstructor - Object constructor used to create new objects with `this.add()`.
  @param {Number} [width] - Width of current map in tiles.
  @param {Number} [height] - Height of current map in tiles.