clearfix(解決浮動高度問題)

參考：http://blog.yam.com/hanasan/article/34569881

/*===========clearfix Str============*/
.clearfix:after{content:".";display:block;height:0;clear:both;visibility:hidden}
.clearfix{display:inline-block;}
/*Hides from IE-mac\*/
* html .clearfix{height:1%;}
.clearfix{display:block;}
/*End hide from IE-mac*/
/*===========clearfix End============*/