Add instructions on how to reproduce viridis

Author: stefanv

README.rst

@@ -30,3 +30,15 @@ Dependencies:
 
 License:
   MIT, see LICENSE.txt for details.
+
+Reproducing viridis
+-------------------
+Load [viridis AKA option_d.py](https://github.com/BIDS/colormap/) using:
+
+```
+python -m viscm --uniform-space buggy-CAM02-UCS -m Bezier edit /tmp/option_d.py
+```
+
+Note that there was a small bug in the assumed sRGB viewing conditions
+while designing viridis. It does not affect the outcome by much. Also
+see `python -m viscm --help`.