cocoa pods安装出错

ERROR:  While executing gem ... (Errno::EPERM)
    Operation not permitted - /usr/bin/update_rubygems

估计是升级系统和安装Xcode7 之后cocoapods不好使了 得升级 一下是解决方案：

自定义GEM_HOME
命令行操作：
$ mkdir -p $HOME/Software/ruby
$ export GEM_HOME=$HOME/Software/ruby
$ gem install cocoapods
　　[...]
　　1 gem installed
$ export PATH=$PATH:$HOME/Sofware/ruby/bin
$ pod --version
　　0.39.0