Add wrapper for JCh->XYZ inverse transformation.

Needs tests, and we still need an M->C converter to get the full inverse pipeline going.
Implement CIECAM02 properly
remove stray print statements
resolved the mystery of the mismatching H values -- the spreadsheet we were using for 'gold' values was definitely wrong
Merge pull request #3 from njsmith/python-ciecam02

Python ciecam02