Resolve Reference Links Correctly

While reprocessing the nodes to change the labels, the refuris should also be
updated, because in the expanded latex the refuris will be used to reference a
cite to its corresponding bibitem and not the labels.

Btw. I don't think it's the optimal solution. It should just be proof of concept.
I am happy to improve the pull request and update unit tests and documentation with some guidance.

With this I think #44 can be closed, which I will do. Please respond here instead of in that issue. Thanks.