Make sensor support running from cpython

[noamraph]

I made sensor.py support cpython, by using time.sleep() if utime.sleep() isn't available.

This allows me to use it from my computer connected to the hub, using https://github.com/noamraph/mindstorms

I also added setup.py, which allows me to pip install spikedev directly from github. It's unrelated, so if you prefer to remove it from the pull request I'll do it.