Mac Lion install ruby1.9.3 and rails 31.3

1. install Xcode（from App Store）
2. install GCC-10.7-v2.pkg
3. install rvm.
     user$ bash -s stable < <(curl -s https://raw.github.com/wayneeseguin/rvm/master/binscripts/rvm-installer)
4. config bash_profile
     $ echo '[[ -s "$HOME/.rvm/scripts/rvm" ]] && . "$HOME/.rvm/scripts/rvm" # Load RVM function'>>~/.bash_profile
5. install ruby 1.9.3
     rvm install 1.9.3
6. install rails 3.1.3
     rvm use 1.9.3
     gem install rails -v 3.1.3 --no-ri --no-rdoc