install_package "yaml-0.1.4" "http://pyyaml.org/download/libyaml/yaml-0.1.4.tar.gz#36c852831d02cf90508c29852361d01b" --if needs_yaml
install_git "rubinius-2.0.0-dev" "https://github.com/rubinius/rubinius.git" "master" rbx