Process other colourmaps

[kwinkunks]

Right now it only works on greyscale VD images, because it turns pixel values into data.

It would be nice to be able to accept other colourmaps, then mapping the colours to a range of data. (If you try a blue-white-red now, you'll get an error because it's transformed to greyscale and then it makes no sense.)

It would be really nice to automagically recognize the colourmap.

Wiggles will obvsly be really hard. See #7

[mycarta]

@kwinkunks remember when I thought we could approach this by training a neural network to identify the main families of colours using cluster analysis?
I just found someone who figured it out for us:
http://blog.zeevgilovitz.com/detecting-dominant-colours-in-python/
https://github.com/ZeevG/python-dominant-image-colour
It's not perfect (I don't see green in the colourmap for the Eiffel tower because it is clustered with brown of trees and leaves) but it is a great start