Create soft_cheerlights.py

[Godzil]

This version have smooth transition when colours changes, making is much nicer to the eyes!

[Gadgetoid]

Good stuff. It would be interesting to see a version that fades directly from one RGB colour to another, rather than translating to the HSV colour space and moving around hue. There's some good discussion of such a thing here: http://stackoverflow.com/questions/21835739/smooth-color-transition-algorithm

[Godzil]

That was on purpose the transition using the Hue, but you have a point, I have some code to do colour gradient, I will look if I can add an option for that :)