组件Clip（play方法的bug）

朱峰

__proto.play=function(from,to){
		(from===void 0)&& (from=0);
		(to===void 0)&& (to=-1);
		this._isPlaying=true;
		this.index=from;
		this._toIndex=to;

this._index++;//源码这里没必要吧

朱峰

__proto._loop=function(){
        if (this._style.visible && this._sources){
            this._index++;//这里又++