COCOAPODS 卸载：
http://blog.csdn.net/qq_18670721/article/details/50432892
COCOAPODS 安装：
http://www.jianshu.com/p/6e5c0f78200a
安装CocoaPods报错 - [!] The dependency `AFNetworking (~> 3.1.0)` is not used in any concrete target.
http://www.cnblogs.com/gongyuhonglou/p/5803144.html
