Update external-domain-checker syntax in README.md
Update external-domain-checker syntax in README.md
enom/buddycloud-server-java,ashward/buddycloud-server-java,surevine/buddycloud-server-java,buddycloud/buddycloud-server-java,enom/buddycloud-server-java,surevine/buddycloud-server-java,buddycloud/buddycloud-server-java,ashward/buddycloud-server-java,webhost/buddycloud-server-java,webhost/buddycloud-server-java