copy and paste in the following command:
/usr/bin/ruby -e "$(curl -fsSL https://raw.github.com/gist/323731)"
It is getting more and more popular to come across such installation recipes. "Just execute this command", which will download some code from the net and run it on your machine. Yes, it's easy and quick but it's terribly insecure, especially without HTTPS. Just take a look at http://npmjs.org . Just imagine the results if npmjs.org gets compromised. This trend is troubling.