level3
Typography:
How can we use bootstraps to make our lead text stand out more?
.lead class
centering text：
using the .text-*
in bootstrap front we have a image library
using icon
the icon looks so small, as bootstrap set font to 14, we need to override it.
we need to add another css file to override
在新建的css 文件里面，我们要重载icon的大小。所有的icon放在新建的features class里面，所有只要改features class 里面的icon。所以千万注意在css文件 选择features, glyphicon class. It's best practice to specific only you need.
adjust icons
操作icon和操作文字一样，改变它的颜色
change the style of the ul element
