移除master源，使用mirrors.tuna.tsinghu

提供pod install的速度，常规操作都会切换到国内的镜像

$ cd ~/.cocoapods/repos 
$ pod repo remove master
$ git clone https://mirrors.tuna.tsinghua.edu.cn/git/CocoaPods/Specs.git tsinghua

添加源

• 添加 官方 CocoaPods Git 源

pod repo add cocoapods https://github.com/CocoaPods/Specs.git

• 添加 清华 CocoaPods 镜像源

pod repo add tsinghua https://mirrors.tuna.tsinghua.edu.cn/git/CocoaPods/Specs.git

• 移除trunk

pod repo remove trunk

• 添加trunk

pod repo add-cdn trunk https://cdn.cocoapods.org/