code: function polygonAppend(polygon, poly, from, to){
      for(var i=from; i<to; i++){
          polygon.push(poly[i]);
      }
  }
docs: Append points "from" to "to"-1 from an other polygon "poly" onto this one.
  @method append
  @param {Polygon} poly The polygon to get points from.
  @param {Number}  from The vertex index in "poly".
  @param {Number}  to The end vertex index in "poly". Note that this vertex is NOT included when appending.
  @return {Array}