效果图：
可以戳这里看效果https://littlehiuman.github.io/menuAndContent/index.html，
= = = = = = = = = 2017/3/10 = = = = = = = = =
改进了：菜单栏的样式，菜单栏自动更新宽度、响应window窗口大小，菜单栏内元素超出长度隐藏，……
效果图：
可以戳这里看效果（刚打开闪一下是因为在更改菜单栏的宽度）https://littlehiuman.github.io/menuAndContent/index2.html，
源码：https://github.com/littleHiuman/