Previously certbot-dns-joker only allowed getting certificates at the root
level of the domain, so, for example, if you owned the domain "example.com"
you could get a certificate for "example.com" or "*.example.com". Now you can
also get a certificate for a subdomain such as sub.example.com. Since
certbot-dns-joker doesn't know how to determine what the root domain is for a
given subdomain you will have to specify the root domain in the credentials
file as "domain = ROOT_DOMAIN".
New Features
* Allow getting certificates for subdomains.