rewrite in Rust

[mcandre]

Optionally rewrite the shell script in Go. This provides more robust error handling, and prepares the application for easier addition of any new normalization features later.

Relates to #3.

[mcandre]

Er, Rust.

Smaller, faster binaries. Similar multiplatform support. Fewer unhandled errors. Functional programming. We already use Rust dev tools, so removing Go simplifies the tech stack.