https://gist.github.com/shu0115/5046345 (这个方法还不一定有效)
http://apple.stackexchange.com/questions/83885/ruby-2-0-0-install-via-rvm-errors-surrounding-openssl 这个我验证的有效。
$ rvm get head --autolibs=3 # get the latest RVM and build required libs
$ rvm requirements # just in case, install all other required stuff
$ rvm reinstall ruby-2.0.0
$ rvm --default use ruby-2.0.0