问题：
/usr/local/bin/pod: /usr/local/Cellar/cocoapods/1.5.3/libexec/bin/pod: /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby: bad interpreter: No such file or directory
/usr/local/bin/pod: line 2: /usr/local/Cellar/cocoapods/1.5.3/libexec/bin/pod: Undefined error: 0

解决办法：
1、首先更新gem
1.1、gem -update --system
1.2、gem -v

2、如果是最新的gem版本，执行下列方法
2.1、gem sources -a https://gems.ruby-china.com
2.3、执行完之后看看有没有输出这个在终端上：https://gems.ruby-china.com added to sources
2.4、执行sudo gem install -n /usr/local/bin cocoapods

3、执行pod install

亲测有效，由于着急写，就没有用MarkDown