WS2812 LED Driver modified by Doug Hilton for RadioShack p/n 2760249 Tri-LED strip

This code updates JonnyMac's nice WS2812 sample 'jm_ws2812' to properly execute on a RadioShack p/n 2760249 Tri-LED strip.
The timing constants are different, but no big deal. The RadioShack LED strip is pretty cool, and I've also tried using the
AdaFruit LED strips which work in a similar manner. I hope this update saves a new coder some time in figuring out these
LED strips. Note that the code for this part number and the newer Radio Shack 2760339 are different in 2 respects.
First, the RGB layout is different and second, the timing constants are different.

73, WD0UG, Doug