ADM Ready, Package.json and minor optimization

Hey Florian,

As the title suggests, I added a few extra things to your otherwise great jQuery plugin.

1. AMD Ready following this method http://stackoverflow.com/a/11890239/641755
2. Add package.json so this can be submitted to jamjs.org etc.
3. Make it work with both `<ul>` and `<ol>` elements.
4. Add example folder with a basic example in it.
5. [Optimize](https://github.com/Ahrengot/stickySectionHeaders/commit/cbfb719c9005a5a64cf02178adbf9d51d7234727#L0L37) and modernize the code (use $.on instead of $.bind) very slightly.