Add a makelistNode function that follows node.js callback conventions

Thanks for your work on this module.  I was trying to use it and I found that the callback conventions for makelist were inconsistent with other node.js modules and it made using libraries like Q hard.  I've added a new API that follows node conventions and did not change the existing API.

I've also attached two other changes that should make contributions from other people a little be easier.  If you don't like the approach of any of the parts, I can submit a new variation.