install ruby 2.0.0-p0 for rbenv or rvm

for mac and rbenv users:

brew update

make sure 2.0.0-p0 in the list

brew upgrade rbenv
brew upgrade ruby-build
rbenv install -l

better to upgrade these library

brew upgrade openssl
brew upgrade readline

export CONFIGURE_OPTS="--with-openssl-dir=brew --prefix openssl --with-readline-dir=$(brew --prefix readline)"

rbenv install 2.0.0-p0

for mac and rvm:
https://coderwall.com/p/tptocq

links:
http://qiita.com/items/05a09296f3633cadac3f
http://d.hatena.ne.jp/hokaccha/20130225/1361751345