add support for Node module

[pdehaan]

It would be nice to be able to run this as a Node module without needing to modify the source.

[ariya]

Implemented in 5dfc9fd.

[kb19]

I believe this breaks integration support for front-end frameworks that are being served using node (i.e. I'm using Thorax with Grunt.js). Maybe including something that checks to see if the 'process' variable is undefined could help.

I've opened a pull request here #31.