Provide a bit more formatting control

I've added some configuration options around font-size and positioning. Also fixed an issue where the node data wasn't being passed back to the colour functions. And made sure there is an ID for each box that isn't 'undefined'.

I also updated the documentation around these things as well.

Initially the code ran through my style rules, so I fixed some missing semi-colons and spacing. I realize that spacing is subjective, so if you aren't interested, feel free to reject the request.