function pathPolygon(r, a0, a1, vangles, cx, cy) {
    var poly = makePolygon(r, a0, a1, vangles);
    return 'M' + transformForSVG(poly, cx, cy).join('L');
}
path polygon

@param {number} r : polygon 'radius'
@param {number} a0 : first angular coordinate in *radians*
@param {number} a1 : second angular coordinate in *radians*
@param {array} vangles : angles of polygon vertices in *radians*
@param {number (optional)} cx : x coordinate of center
@param {number (optional)} cy : y coordinate of center
@return {string} svg path