function optionKeyFromName(name) {
    return name.replace(/-/g, '_');
}
Transform an option name to a "key" that is used as the field
on the `opts` object returned from `<parser>.parse()`.

Transformations:
- '-' -> '_': This allow one to use hyphen in option names (common)
  but not have to do silly things like `opt["dry-run"]` to access the
  parsed results.