Release version 0.8.9:

- Updated bundled libfluidsynth on MacOS to HEAD version (3.0.1) to fix CoreAudio issue on BigSur/M1 chip.
- Rewrote easy setup section of documentation
- Tested support for abjad 3.4. Currently both 3.3 and 3.4 should work with SCAMP, with very minor cosmetic differences in lilypond formatting.
- Fixed an internal bug with scaling of MIDI CC messages. Statements like `oboe.play_note(70, 0.7, 1.0, {"param_10": [0, 1, 0, 1, 0]})` should now work to have the note oscillate between left and right channels. (Since MIDI CC 10 is pan, and SCAMP works with ranges from 0 to 1.)
- Fixed bug with parsing of additional playback properties
- Fix for minor bug when calculating staff length for staves with empty voices