Adafruit-circuitpython-rfm9x

We have upgraded Pylint checks to use the latest version of Pylint and implemented usage of Black Python formatting. This does not change the functionality of the code - it is designed to bring it up to current standards and make it more readable.

* Remove pinned Pylint version number from build.yml file
* Synced `.pylintrc` file to match Adafruit standard
* Ran upgraded Pylint and applied any changes or new disables necessary
* Ran Black formatter and allowed application of changes across entire repo

For more information on using Pylint and Black on your code, check out [this guide on working with Pylint and Black](https://learn.adafruit.com/improve-your-code-with-pylint)

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

To use in CPython, `pip3 install adafruit-circuitpython-rfm9x`.

Read the [docs](http://circuitpython.readthedocs.io/projects/rfm9x/en/latest/) for info on how to use it.

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

To use in CPython, `pip3 install adafruit-circuitpython-rfm9x`.

Read the [docs](http://circuitpython.readthedocs.io/projects/rfm9x/en/latest/) for info on how to use it.

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-rfm9x`.

Read the [docs](http://circuitpython.readthedocs.io/projects/rfm9x/en/latest/) for info on how to use it.

* https://github.com/adafruit/Adafruit_CircuitPython_RFM9x/pull/33 `send` and `receive` methods modified to allow interrupts from user-code.
* [Example of usage with Raspberry Pi](https://github.com/adafruit/Adafruit_CircuitPython_RFM9x/blob/master/examples/rfm9x_rpi_interrupt.py)

* https://github.com/adafruit/Adafruit_CircuitPython_RFM9x/pull/33 `send` can now listen after a packet is sent using new kwarg `keep_listening`
* [Example of usage on Microcontrollers](https://github.com/adafruit/Adafruit_CircuitPython_RFM9x/blob/master/examples/rfm9x_transmit.py).

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-rfm9x`.

Read the [docs](http://circuitpython.readthedocs.io/projects/rfm9x/en/latest/) for info on how to use it.

* Repo URL updated to the correct URL for compatibility with `circup`, thanks ntoll

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-rfm9x`.

Read the [docs](http://circuitpython.readthedocs.io/projects/rfm9x/en/latest/) for info on how to use it.

* Incorrectly setting `tx_power` and `frequency_mhz` throws errors describing the accepted range
* RFM9x now checks version to verify correct wiring

Thanks terriko!

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-rfm9x`.

Read the [docs](http://circuitpython.readthedocs.io/projects/rfm9x/en/latest/) for info on how to use it.