升级系统之后发现原来的pod install 等方法不管用了，提示如下错误：
-bash: /usr/local/bin/pod: /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby: bad interpreter: No such file or directory
方法是安装更高版本的源。
1.you need to read all the texts that are displayed when you install RVM，remove the old rvm first
rm -rf ~/.rvm
curl -L https://get.rvm.io | bash -s stable
See：https://stackoverflow.com/questions/11677771/rvm-command-not-found-mac-ox
如果没删除原有的源，在接下来的步骤当你执行 rvm 操作时会提示如下错误：
2.you need to close the terminal ,then open again!
3.安装新版ruby
command rvm install 2.3.0
4.使用下载好的ruby作为默认ruby源
rvm use 2.3.0 --default
5.安装cocoapods
sudo gem install -n /usr/local/bin cocoapods
接下来就可以执行常见的pod操作命令了。
cd 到指定目录 安装pod
pod install
See：http://blog.csdn.net/sharktoping/article/details/52311460
https://stackoverflow.com/questions/11677771/rvm-command-not-found-mac-ox
