Added note about the custom ``UNIQUE (`ip`, `nameserver`)`` restriction in SuperMaster model.
Added note about the custom ``UNIQUE (`ip`, `nameserver`)`` restriction in SuperMaster model.

kumina/django-powerdns-manager,d9pouces/django-powerdns-manager,gnotaras/django-powerdns-manager,kumina/django-powerdns-manager,gnotaras/django-powerdns-manager,d9pouces/django-powerdns-manager