added start of hardware design doc
added start of hardware design doc

idcrook/rpi-iot-demo-2017,idcrook/rpi-iot-demo-2017,idcrook/rpi-iot-demo-2017,idcrook/rpi-iot-demo-2017,idcrook/rpi-iot-demo-2017,idcrook/rpi-iot-demo-2017