code: function _quadTree(bounds, level, maxElements, maxLevel) {
      return {
        level: level || 0,
        bounds: bounds,
        corners: _geom.splitSquare(bounds),
        maxElements: maxElements || 20,
        maxLevel: maxLevel || 4,
        elements: [],
        nodes: []
      };
    }
docs: Creates the quadtree object itself.
  
  @param  {object}   bounds       The boundaries of the quad defined by an
  origin (x, y), width and heigth.
  @param  {integer}  level        The level of the quad in the tree.
  @param  {integer}  maxElements  The max number of element in a leaf node.
  @param  {integer}  maxLevel     The max recursion level of the tree.
  @return {object}                The quadtree object.