Add driver for Adafruit strands with LPD8806 chipset

Here's a driver for the LPD8806 chipset which is used in Adafruit's LED strands:
http://www.adafruit.com/products/306

I started from our existing WS2801 driver and modified it to speak the LPD8806's protocol which is documented in Adafruit's official Arduino library:
https://github.com/adafruit/LPD8806/blob/master/LPD8806.cpp