Save this file as Node.sublime-build in your User folder, which you can get to by going to menu tree Sublime Text 2 > Preferences > Browse Packages....
It fixes a file path problem I was having using this solution: http://logicmason.com/2013/adding-a-js-build-system-to-sublime/comment-page-1/
It should automatically set the build system for all .js files but if it doesn’t, go to Tools > Build System > Node.