FCC-Front End Development Responsive Design with Bootstrap

因为这节讲的内容会是利用Bootstrap制作一个响应式的网页，所以它的内容很实际！
知识点：

1. text-center类，可以让文字居中对齐。
2. container-fluid, container是栅格系统最外层的容器。
3. btn类,bootstrap中按钮的基础类。
4. btn-block让button占据屏幕所有宽度。
5. btn-primary，btn-info，btn-danger上色类
6. 栅格系统，row，col-xs-*,col-md-&*,col-sm-*.
7. text-primary，text-danger，bootstrap中给文字上色。
8. font-awesome: You can add Font Awesome to any app just by including it by adding the following code to the top of your HTML:<link rel="stylesheet" href="//maxcdn.bootstrapcdn.com/font-awesome/4.5.0/css/font-awesome.min.css"/>. And the i element was originally used to make other elements italic, but is now commonly used for icons. You add the Font Awesome classes to the i element to turn it into an icon, for example:<i class="fa fa-info-circle"></i>