Remove quickstart example

Removed quickstart example and provided a link to a gist instead.
Remove /var/log/ volume
Update README.md
Add IP_ADDR environement variable

Added the IP_ADDR environment variable in order for supervisorctl to listen on that address.
Add supervisorctl support
Add port 9001

Added port 9001 for the listening port of supervisorctl.
Merge branch 'feature/log' into develop
Change environment variable name
Add SUPERVISOR_PASSWORD environment variable
Update README.md
Fix SMTPS protocol

Added SASL authentication via dovecot.