Docker CAS steps

• docker run -d --name cas -p 8443:8443 apereo/cas:v6.1.3
• [optional] docker logs cas, "<The following profiles are active: standalone>" shown.
• append "127.0.0.1 cas.example.org" to /etc/hosts
• visit https://cas.example.org:8443/cas
• login username: casuser, password Mellon