Added npm stuff, slightly updated README file.

I've converted the `karotz.js` file to an npm module and added some other missing files, such as `package.json`, `.gitignore`, …

Basically you can merge this pull request and afterwards publish the module to the central npm repository using:

    $ npm publish

As name for the module I'd suggest `karotz` (which actually is available), and this name is already configured in `package.json`. This way you could install the module by simply typing

    $ npm install karotz

and all the dependencies would be resolved automatically. Then you'd be able to import it to your project by using

    var karotz = require('karotz');

Hope you like it :-)