Merge pull request #86 from nitsch/master

Added request types and new utility for testing the challenge-response s...
Moved retrieval of Move's serial to happen prior to switching to DFU mode. It won't retrieve anything otherwise since the Move will not act as HID anymore in this mode.
Added optional switch --btdfu to the psmove_dfu_mode utility. This allows switching to BTDFU mode, not only STDFU mode as before.