Added initial support for Beagle Bone Black
Added initial support for Beagle Bone Black

A new set of GPIOs built with info from the Beagle Bone Reference Manual
(https://github.com/CircuitCo/BeagleBone-Black/blob/master/BBB_SRM.pdf)
has been added.

The map's keys are not really that useful when the user will try to
retrieve a specific gpio, a better solution is needed.

stephanmantler/SwiftyGPIO,uraimo/SwiftyGPIO,stephanmantler/SwiftyGPIO,uraimo/SwiftyGPIO,colemancda/SwiftyGPIO