Add simplistic KSP version detection.

Benefits #
49
 #48. This just peeks in the readme file.
Appears to work on 0.23.5, 0.24.2, and 0.25.0.

I'm not sure if there's a better way to throw our exception
with this. Suggestions welcome. (Other than returning null,
which was a leading cause of accidents when I worked in the code mines.)