A quick word of warning for anyone following this guide. You should never sudo npm install. That's giving root privileges to anyone that care's to upload code to the npm package registry. npm should work fine without sudo.
See also: http://cristianobetta.com/blog/2013/02/02/ruby-gems-are-not-...
lol
1) That English is the poster's native language
2) the poster did not use auto-correct