实现无限循环滚动的UIScrollView，可以设置不同的滚动速度。自动滚动时，两列滚动视图的滚动速率是一样的。当用手指滚动某一列时，两列滚动视图的滚动速率是不同的 -Achieve infinite loop scrolling UIScrollView, you can set different scrolling speed. Automatic scroll, the two rows of rolling rate is the same view of the rolling.