I've added full directional control and the ability to specify something besides the joining distance for the vertical axis. I've also changed things so that the program doesn't use linestyle='steps' to make the branches, as a result you now have the ability to specify line styles for different branches in addition to color (useful if you're publishing in black & white).
If anyone has any suggestions for additional features they'd like to see, let me know and I'll see what I can do. If you'd like to write your own modifications, feel free to pass them along to me and I'll post an updated version that includes your modifications.
R. Padraic Springuel
Department of Physics and Astronomy
University of Maine
Office Hours: Wednesday 2-3pm