CocoaPods 本来作为一个第三方库管理工具，有的时候总是出现各种莫名其妙的问题，最近遇到一个问题就是:
The `master` repo requires CocoaPods 1.0.0 - (currently using 0.39.0)
中间折腾了很久，受启发的有两篇文章:
http://blog.cocoapods.org/Sharding/
cd ~/.cocoapods/repos/master/
git fetch origin master
git checkout v0.32.1
CocoaPods 0.39.0 不能setup不能通过原本的source "https://github.com/CocoaPods/Specs.git" 进行更新，需要指定Tag，0.32.1.
另外一篇文章https://github.com/CocoaPods/CocoaPods/issues/6164,解决方案与上面类似:
cd ~/.cocoapods/repos && git clone https://github.com/CocoaPods/Specs.git && cd specs && git checkout v0.32.1)
, or upgrade to CocoaPods > 1.0
