在Mavericks下安装Cocoapods遇到ruby安装问题，参照以下网址圆满解决问题。
http://www.moncefbelyamani.com/how-to-install-xcode-homebrew-git-rvm-ruby-on-mac/#step-7
https://github.com/dewind/cocoapods
http://phpadvocate.com/blog/2013/08/things-to-watch-out-for-when-installing-cocoapods/
https://github.com/CocoaPods/CocoaPods/issues/693
http://blog.zerosharp.com/installing-ruby-with-homebrew-and-rbenv-on-mac-os-x-mountain-lion/