Idiomatic Rust and misc. updates

[Riceman2000]

There are a few things that I would like to change about the source code of this project to make it follow some of Rust's idioms.

• Split the functional code into a Library Crate so it could be used by others
  • After this change consider uploading to crates.io
• Error handling appropriate for a library using std::log -> https://docs.rs/log/latest/log/
  • Also critical errors should not panic, instead they should pass that error back
  • An error type for the library could be made to make this easier with thiserror https://docs.rs/thiserror/latest/thiserror/
• Some unit testing
  • Incorporate testing into pipeline

Saw the YouTube video and I'd love to contribute, I'll submit a PR with a few changes.

Thanks!

[brasky]

Copying over from your PR #3 to track

Things still left to do if anyone is feeling up to it:

• Add benchmarks
• Benchmark across some different optimization settings
• Write docs for the code -> https://doc.rust-lang.org/rust-by-example/meta/doc.html
• Examples/doctests for those looking at is as a library
• Decide the easiest way to execute this code

Currently I left it as
use nmuidi::prelude::*;
...
Cleaner::new("/test/path").clean()
...
It could be simpler if we change some things around but that could close the door on other functionality 🤷

[brasky]

Just published it as a crate
https://crates.io/crates/nmuidi