Move my default i2c init routine into i2c_helper.h
Add some WS2812B communication helpers
Add LED_ASSERT - pulse a pin when an assert fails
Implement a Wii Nunchuk RC transmitter slave

The input from the Wii Nunchuk is processed and translated into PPM
signals that are sent to the slave port of a RC transmitter, like the
Spektrum DX8. The DX8 then handles all the RF communication to a RC
receiver in, for example, a Blade Nano QX quadcopter.
Renamed wii_nunchuck.h to wii_nunchuk.h
Fixed name Nunchuck to Nunchuk
Update Nunchuk reference comments