LTPopButton 通过 Facebook Pop 实现的动态按钮。有增加、减少、关闭、菜单、返回、下一步等多种按钮。
使用方法：
LTPopButton *button = [[LTPopButton alloc]initWithFrame:CGRectMake(100, 100, 36, 30)]; [self.view addSubview:button]; [button animateToType:menuType]; // there are various types, see examples
