Detect compatible `wasm-opt` versions and improve error messages (#242)

* Improve `wasm-opt` not found error message

* Improve error message + check `wasm-opt` compatibility

* Use `regex` for parsing `wasm-opt --version`

* Apply suggestions from code review

Co-authored-by: Andrew Jones <ascjones@gmail.com>

* Implement comments

* Apply cargo fmt

Co-authored-by: Andrew Jones <ascjones@gmail.com>