WIP: Rust port

[kylebarron]

for #2

This compiles but I probably made a mistake in porting the color scale conversion functions and so it's giving incorrect values as output.

I can't seem to install the cython version, so I didn't take time to try and track down where the incorrect change was

You can test this with

cd rust
virtualenv env
source ./env/bin/activate
pip install maturin
maturin develop

(you need Rust installed) then

from color_operations import saturate_rgb

[kylebarron]

We added one test for RGB color saturation (from rio-color) and it's working! So it turns out that the code very likely did originally work, but that setting a satmult of 50 was too high and it saturated the colors all the way to 0, 1, 1

[kylebarron]

Closing in favor of #8