IOS cocoapods安装

1. 安装cocoapads：sudo gem install cocoapods
   
   需要更换源地址：
   添加源：gem sources --add https://gems.ruby-china.com/
   删除源：gem sources --remove http://rubygems-china.oss.aliyuncs.com
   查看源：gem sources -l
   
   再次执行安装命令：sudo gem install cocoapods
   
   执行：sudo gem install -n /usr/local/bin cocoapods
   
2. 设置pod仓库：pod setup
   参考：执行pod setup很慢很慢解决方案： https://www.jianshu.com/p/43a268ba8f47