Normalize.css：优化重置CSS默认属性
官方网站：http://necolas.github.io/normalize.css/
项目仓库：https://github.com/necolas/normalize.css/
下载方法:
NPM
npm install --save normalize.css
Bower
bower install --save normalize-css
CDN
See https://cdnjs.com/libraries/normalize
Download
See https://necolas.github.io/normalize.css/latest/normalize.css