Consider moving to the cobra module

[acidprime]

This CLI was a little confusing to me as long arguments used a single dash instead of two and when using two it didn't give an error. I have had great success with the Cobra I think with its built in modern standards and auto complention it might be a good update for this projects ease of use.

[Mic92]

Go's own parser also supports -- actually: https://github.com/numtide/nixos-facter/blob/4386a33b033f846de055ee32a1ddb0fd8ae270f2/cmd/root.go#L74

I would like to avoid big dependencies because most of the maintenance work actually comes from having to bumping libraries.