New release with improved dependencies installation instructions

Prepare for release 2.0.3

Fix version in `setup.cfg` & `README.md`.

Fix 0 being interpreted as None for CC events value

Use released version for pyalsa

Fixed setup version and categories (#35)

Show app version in MIDI select dlg (#33)

Update for release 0.7.0

Release 0.6.0

Tag 0.5.0 (#20)