Updated docs and semver versioning.
To use in CircuitPython, download the .mpy file and copy it to the `lib` folder on the `CIRCUITPY` drive. Or, simply install the [Adafruit CircuitPython bundle](https://github.com/adafruit/Adafruit_CircuitPython_Bundle).
Read the [docs](http://circuitpython.readthedocs.io/projects/hcsr04/en/latest/) for info on how to use it.