/**
     * Takes the collision data defined in the collision editor of Tiled and applies it to
     * and exisiting tilemap for use with P2 physics bodies.
     *
     * Tilemap json data MUST be loaded in the Preload state/function using game.load.json() before this function is called
     * map must only have ONE tileset
     * each tile can only have ONE polyline set for it's collision
     * the polyline MUST be a complete shape (the last point is indentical to the first)
     *
     * @param {Phaser.Tilemap} map - this is the map which you want polylines added to
     * @param {string} key - this is the key for the raw json tilemap data loaded in the preload state
     * @param {bool} [roundValues=true] - Will round the x,y coordinates for the polylines to nearest integer
     */
    addPolylineCollision: function (map, key, roundValues) {

        if (roundValues === undefined) { roundValues = true; }

        // json with the collision data that was omitted by phaser
        let data = this.game.cache.getJSON(key);
        //console.log(data);
        let collisionData = data.tilesets[0].tiles;
        // array of the collision polygons that will get added to the tilemap
        var polygons = [];
        // tiles in the Collision Layer that will help define the polygons
        let mapData = map.layers[map.getLayer('Collision Layer')].data;
        for (let row in mapData) {
            for (let col in mapData[row]) {
                var wall = collisionData[mapData[row][col].index - 1];
                if (wall !== undefined) {
                    for (let i in wall.objectgroup.objects) {
                        let poly = {
                            height: 0,
                            name: "",
                            polyline: [],
                            properties: undefined,
                            type: "",
                            visible: true,
                            width: 0,
                            x: mapData[row][col].x * map.tileWidth,
                            y: mapData[row][col].y * map.tileHeight
                        };
                        for (let j in wall.objectgroup.objects[i].polyline) {

                            var coords = [wall.objectgroup.objects[i].polyline[j].x,
                                          wall.objectgroup.objects[i].polyline[j].y];
                            if (roundValues) {
                                coords[0] = Math.round(coords[0]);
                                coords[1] = Math.round(coords[1]);
                            }
                            poly.polyline.push(coords);
                        }
                        polygons.push(poly);
                    }
                }
            }
        }
        console.log(polygons);
        map.collision['Collision Layer'] = polygons;
    }
};