Error running 'requirements_osx_brew_libs_install gcc49 libyaml libksba openssl
brew install autoconf
brew install automake
brew install libtool
brew install apple-gcc42
brew install libyaml
brew install libxslt
brew install libksba
brew install openssl
rvm requirements
查看目前的所有ruby版本：
rvm list known
rvm instatll .3.3.3
rvm 3.3.3 -default
rvm remove 3.3.3
备注：苹果系统升级OSX10.11EICapitan后安装改为:
sudo gem install -n /usr/local/bin cocoapods
