small bug fixes
refactor drivers
Merge branch 'drivermanager' of github.com:danielkummer/nixon-pi into drivermanager

Conflicts:
	lib/nixonpi/drivers/bar_graph_driver.rb
	lib/nixonpi/drivers/io_driver.rb
	lib/nixonpi/drivers/power_driver.rb
	lib/nixonpi/state_machines/lamp_state_machine.rb
	lib/nixonpi_service.rb