gunicorn 20.0.0 included a change so that it will no longer read server
configuration out of Paster files. Because of this, the settings for it
in development.ini and production.ini were no longer being used. This
resulted in the auto-reloading no longer working in dev, and the number
of workers being reduced back down to 1 in production. The socket/PID
may have been impacted as well.
This commit moves the configuration into command-line args used to
launch gunicorn, and uses a pillar variable to handle the args different
between dev and prod.