https://philipwalton.github.io/solved-by-flexbox/
http://www.ruanyifeng.com/blog/2015/07/flex-grammar.html?utm_source=tuicool
http://www.ruanyifeng.com/blog/2015/07/flex-examples.html
flexbox学习
原文：http://www.cnblogs.com/lummon/p/5950095.html
