地址：https://github.com/dustylove/ruler
Untitled.gif
使用方法：
ScrollRulerView *ruler = [[ScrollRulerView alloc]initWithFrame:CGRectMake(0, 200, self.view.bounds.size.width, 100) Unit:100 Max:20000 Defalt:1000 block:^(NSInteger value) {
label.text = [NSString stringWithFormat:@"滑到%ld了",value];
}];
ruler.follow = YES;//同步变化
