Din99 DeltaE

[o1lo01ol1o]

This ports the LAB to DIN99 and delta E metric from https://github.com/colour-science/colour. There may be some issues on the docstrings (they fail due to floating point errors on some platforms) and there's an API question of how to handle the kH and kCH parameters. Partially addresses #1

[lehins]

This is a really great start. Thank you for doing this. Requests to change are mostly cosmetic.

I'll ponder a little on the way to add ability to supply extra parameters to color space conversions. This will definitely need a slight change to the api

[lehins]

That's a good start for DIN99. Thank you.

I'll try to figure out later how we can adjust the api to supply extra options during color space conversion.

[lehins]

I think a bad import is the last thing

[lehins]

@o1lo01ol1o Thank you!