cocoapods2017升级

1、更新gem：sudo gem update --system

2、以前的淘宝镜像没用了，得移除掉：gem sources --remove https://ruby.taobao.org/  

3、修改新的镜像：gem sources -a https://gems.ruby-china.org

4、gem sources -l  然后查看gem sources源是不是 https://gems.ruby-china.org

5、升级cocoapods：sudo gem install -n /usr/local/bin cocoapods --pre

6、查看升级后的cocoapods版本：pod --version