/**********************************************************************
* bootstrap 4 pull-right无效
* 说明：
* 在测试bootstrap的时候发现pull-right无效，原来是已经换成了float-right。
*
* 2018-4-25 深圳 宝安西乡 曾剑锋
*********************************************************************/
一、参考文档：
1. What happened to the .pull-left and .pull-right classes in Bootstrap 4?
https://stackoverflow.com/questions/39655110/what-happened-to-the-pull-left-and-pull-right-classes-in-bootstrap-4
2. pull-right replacement in bootstrap 4 does not work
https://stackoverflow.com/questions/46221635/pull-right-replacement-in-bootstrap-4-does-not-work
二、解决办法：
The classes are currently float-right float-sm-right etc.
