Minor bugfixes especially to wrapper

While incorporating myradex into [pyradex](https://github.com/keflavich/pyradex), I found a few minor bugs and one fairly significant one.

The important error is that the collisional partner is not necessarily indicated in the text string description on the collision partner line: instead, there is a number indicating which partner is intended.

I also added a new parameter to the interactive mode to allow user specification of the geometry.