Add combinator for working with ColorStops

[safareli]

I have used this two combinators for working with ColorStops here

combineStops :: Number → ColorStops → ColorStops → ColorStops
reverseStops :: ColorStops → ColorStops

--  usage:
myStops = fooStops `combineStops 0.5`  (reverseStops fooStops)

[sharkdp]

So combineStops basically concatenates two color scales and the Number defines the transition point (i.e. is a number between 0 and 1)?

Sounds good!

[safareli]

yap