Move to no_std?

[Qix-]

Hi there,

Is there any chance of transitioning this to a no_std crate? I haven't scoured the sources enough to see whether or not this would be a trivial change, but I would imagine at least the core color structures and model conversion algorithms would be no_std-able at the very least.

Would be happy to put in a PR if it is given the green light.

Thanks!