Gemfile

source 'https://rubygems.org'
ruby "2.0.0"

gem 'rails',     github: 'rails/rails'
gem 'arel',      github: 'rails/arel'
...

terminal.bash

rvm get head

# For Debian-based systems
apt-get install libyaml-dev

# For Mac with Homebrew
brew install libyaml

rvm pkg install openssl
rvm install 2.0.0 \ 
    --with-openssl-dir=$HOME/.rvm/usr \
    --verify-downloads 1
rvm use 2.0.0