Fix object conversions (#47)

Fix object conversions

Adding support for MIDI 2.0 protocol (#36)

Migrated CI to GitHub Actions && PacketBuffer improvements

- Rust compiler upgraded to 1.51.0
- Rust edition upgraded to 2018
- Upgrade coremidi-sys, core-foundation and core-foundation-sys
- Moved `struct`s and `impl`s together
- `PacketBuffer` uses `MIDIPacketListInit` and `MIDIPacketListAdd`
- Applied cargo fmt
- Several Clippy fixes
- Migrated CI to Github Actions
- **Breaks retro-compatibility for notification events**
   - `IOErrorInfo` renamed to `IoErrorInfo`
   - `Notification::IOError` renamed to `Notification::IoError`

Documented How to Receive Client Notifications (#28)

implement Send for BoxedCallback (#15)

Allow empty PacketBuffer and initial capacity

PacketBuffer rewrite

Correct lifetime for callback

First beta release

Added input ports support with callbacks and a packet builder.