feat: argument bounds checking and option filtering

[cjdjpj]

Argument bounds checking: make sure float values for frequencies are valid, panic otherwise.

Option filtering: refactored filtering to use Option type rather than throw an error

[jeffersonfparil]

Nice. Thanks. Just keep in mind we'll need to redefine these ErrorKind's into some custom Error type which we can chain in the future.

[cjdjpj]

Right, I am going to do this right after. What do you mean by chaining errors? All I had in mind was a couple (2-4) error structs that encompassed most of the current "errors" and implementing unique display methods for each of them.

[jeffersonfparil]

If one error caused another in a cascade, we need to chain them to identify the root cause. I have not looked too hard into implementing this manually, but I believe the anyhow crate implements this. You may use that crate for all the error handling-related stuff or you may implement things yourself from scratch.