Adafruit-circuitpython-max31855

This release includes:
* Migrating this repository from Travis to GitHub Actions. This has no effect on the behavior of the code itself.

To use in CircuitPython, simply install the [Adafruit CircuitPython bundle](https://circuitpython.org/libraries).

To use in CPython, `pip3 install adafruit-circuitpython-max31855`.

Read the [docs](http://circuitpython.readthedocs.io/projects/max31855/en/latest/) for info on how to use it.

* Added `temperature_NIST` which uses raw voltages and NIST curve fit coefficients for type K.

To use in CircuitPython, simply install the [Adafruit CircuitPython bundle](https://circuitpython.org/libraries).

To use in CPython, `pip install adafruit-circuitpython-max31855`.

Read the [docs](http://circuitpython.readthedocs.io/projects/max31855/en/latest/) for info on how to use it

* Fixed conversion factor for reference temperature.

To use in CircuitPython, simply install the [Adafruit CircuitPython bundle](https://github.com/adafruit/Adafruit_CircuitPython_Bundle).

To use in CPython, `pip install adafruit-circuitpython-max31855`.

Read the [docs](http://circuitpython.readthedocs.io/projects/max31855/en/latest/) for info on how to use it.

To use in CircuitPython, simply install the [Adafruit CircuitPython bundle](https://github.com/adafruit/Adafruit_CircuitPython_Bundle).

To use in CPython, `pip install adafruit-circuitpython-max31855`.

Read the [docs](http://circuitpython.readthedocs.io/projects/max31855/en/latest/) for info on how to use it.

To use in CircuitPython, simply install the [Adafruit CircuitPython bundle](https://github.com/adafruit/Adafruit_CircuitPython_Bundle).

To use in CPython, `pip install adafruit-circuitpython-max31855`.

Read the [docs](http://circuitpython.readthedocs.io/projects/max31855/en/latest/) for info on how to use it.

Fixed badge, added update to force use of desired `pylint` version.

To use in CircuitPython, simply install the [Adafruit CircuitPython bundle](https://github.com/adafruit/Adafruit_CircuitPython_Bundle).

To use in CPython, `pip install adafruit-circuitpython-max31855`.

Read the [docs](http://circuitpython.readthedocs.io/projects/max31855/en/latest/) for info on how to use it.