Allow returning pressure readings outside the documented 300hPa - 1100hPa full accuracy range, so that pressure can continue to be read, at reduced accuracy. Thanks gbaman.
To use in CircuitPython, simply install the [Adafruit CircuitPython bundle](https://circuitpython.org/libraries).
To use in CPython, `pip3 install adafruit-circuitpython-bme280`.
Read the [docs](http://circuitpython.readthedocs.io/projects/bme280/en/latest/) for info on how to use it.