In initialize( ), we establish the connection between the Arduino and the
Nunchuk by sending a handshake. In line 8, we call Wire’s begin( )
method, so the Arduino joins the I2C bus as a master (if you pass
begin( ) an ID, it joins the bus as a slave having this ID). Then we begin
a new transmission to the device identified by NUNCHUCK_DEVICE_ID: our
Nunchuk.