Added a helper function `set_iaq_relative_humidity()` to set humidity compensation based on temperature and relative humidity. Thanks benthorner!
To use in CircuitPython, simply install the [Adafruit CircuitPython Bundle](https://circuitpython.org/libraries).
To use in CPython, `pip3 install adafruit-circuitpython-sgp30`.
Read the [docs](http://circuitpython.readthedocs.io/projects/sgp30/en/latest/) for info on how to use it.