code: function(sx, sy) {
                  this.callBase({
                      beginValue: 0,
                      finishValue: 1,
                      setter: function(target, value, timeline) {
                          var delta = timeline.getDelta();
                          var kx = Math.pow(sx, delta);
                          var ky = Math.pow(sy, delta);
                          target.scale(ky, kx);
                      }
                  });
              }
docs: @constructor
  @for kity.ScaleAnimator
  
  @grammar new kity.ScaleAnimator(sx, sy)
  @param  {Number} sx x 轴的缩放比例
  @param  {Number} sy y 轴的缩放比例