Packaged RoyGBiv

Hi Giv,

Thanks for the excellent work. We are using this module so I thought it might be worth to package it so that it can be pip installable. 
Apart from packaging changes I have made following minor changes to roygbiv.py (now roygbiv/__init__.py). 
- tabs -> spaces
- Modified Roygbiv class to accept image or filename. This avoids reopening image in case ImageFile object is already initialized

Hope you are fine with this. Please do take a look at setup.py for your licensing/credits preferences. If all goes fine would you want to push it to pypi. I don't mind volunteering for the same.

Thanks again.
Shekhar