resume() {
    if (this.paused && this.playing) {
      this.paused = false;
      if (this._onResume !== undefined) {
        this._onResume.call(this);
      }
      // re-queue execution context
      queueStart.call(this);
      // update time and let it roll
      this._startTime += KEC.Time() - this._pauseTime;
      add(this);
      // restart ticker if stopped
      if (!Tick) Ticker();
    }
    return this;
  }
Resume tweening
@returns {Tween} this instance