Automatic Nunchuk Reinit & Speedup

1: If only 0xFF is received from the Nunchuk a reinit is automatically
attempted.  2: If only partial data is received the sensor values won't
be updated.  3: The transmission delay was moved to init() only.  I'm
not sure how much of a delay is needed in the init, but program code
should provide the delay at the end of update().  This sped my program
up significantly, from processing at 40FPS to 80FPS.