Version 0.2.1

This release is mostly updates of dependencies and will be the last
release to feature support for SPI devices.

Version 0.2.0

* Add GPLv3 license
* hexws2811: Fix performance issues
* generic: Add support for 1-byte RGB and 1-bit grayscale formats
* Remove deprecated --linger, use --exit never instead
* Make the missing --geometry message easier to understand
* Document transpositions with just text diagrams
* artnet: Add a flag to set the DMX universe
* Add a new exit condition to exit when at least one input closes
* fluxled: Allow connections to fail
* simulator: Fix the bottom row not being shown for odd heights
* Prefer no driver instead of aborting when the driver could not be detected
* generic: Add pixel formatting options
* Document 'show' device type

- Slightly speed up I/O
- driver/generic: Drastically speed up outputting over stdout
- Add basic support for LED Matrices through Hzeller's library (manual builds only)
- Fix some minor things found by clippy
- Add support for some kind of FluxLED device

- Add support for Mac OSX
- Add support for the SK9822
- Minor fixes