Changd led update functions to return pixel arrays
Changd led update functions to return pixel arrays

Led update functions now return an array of pixel values instead of
updating the LED strip directly.  This change makes it possible to
combine the effects of different LED update functions before updating
the LED strip. The function responsible for updating the LED strip is
led_visualization()

joeybab3/audio-reactive-led-strip,scottlawsonbc/audio-reactive-led-strip,scottlawsonbc/audio-reactive-led-strip,joeybab3/audio-reactive-led-strip