Added LPD8806 driver.

Squashed commit of the following:

commit bfec70f6ce035e4243ee839a33e444c016ebc4a8
Author: Joe Kroesche <joe@kroesche.org>
Date:   Sun Jul 27 15:04:48 2014 -0500

    Work on docs, minor fixes found from testing

commit eebfb7676a52ae915d553e6992e623e8303e826a
Author: Joe Kroesche <joe@kroesche.org>
Date:   Sun Jul 27 14:55:30 2014 -0500

    Reworked LPD8806 driver API

commit 2b80033db7ee6887258688d3d36783787822cf76
Author: Joe Kroesche <joe@kroesche.org>
Date:   Sun Mar 16 11:07:16 2014 -0500

    First iteration of lpd8806 driver, works okay