code: function Edge(current, next) {
  
    /**
     * @type {Object}
     */
    this.current = current;
  
    /**
     * @type {Object}
     */
    this.next = next;
  
    /**
     * @type {Object}
     */
    this._inNormal  = this.inwardsNormal();
  
    /**
     * @type {Object}
     */
    this._outNormal = this.outwardsNormal();
  }
docs: Offset edge of the polygon
  
  @param  {Object} current
  @param  {Object} next
  @constructor