NodeJS support - npm package - tests

Hi, 

I added nodejs support for your library and prepared it for publishing to npm. Just go into the directory and use `npm publish`. See https://npmjs.org/doc/publish.html.

I also added two simple tests with [mocha](https://github.com/visionmedia/mocha). Use `mocha -R spec` inside the project directory to run the tests. The project is also prepared to to run the tests on http://travis-ci.org.