[Feature Request] Python 3 support

[dieseltravis]

I am not sure what is involved with updating unfortunately.

~ $ python3 /usr/local/bin/listen-for-shutdown.py
Traceback (most recent call last):
  File "/usr/local/bin/listen-for-shutdown.py", line 4, in <module>
    import RPi.GPIO as GPIO
ModuleNotFoundError: No module named 'RPi'

[dieseltravis]

I think I fixed it locally by running this:
sudo apt-get install python3-rpi.gpio