show yes/no at a shell prompt
$ yesno && echo done.
continue? [y/N]: n
$ yesno && echo done.
continue? [y/N]: y
done.
$
--message value, -m value specify message (default: "continue?")
--yes, -y set default to yes
--help, -h show help
--version, -v print the version
0.1.0