Consider introducing poliastro as a dependency

[astrojuanlu]

I stumbled upon this project via the SGAC mailing list. I checked the script that plots the orbit and found many algorithms that are already implemented in my Python open source library poliastro:

http://poliastro.readthedocs.io/en/latest/

There are several examples, including 3D plotting:

http://nbviewer.jupyter.org/github/poliastro/poliastro/blob/master/examples/Going%20to%20Mars%20with%20Python%20using%20poliastro.ipynb

If you consider using it, I will be happy to accept feature requests and adapt the library to your needs.