Stack update

[dhsathiya]

Need to update the Docker images available on https://github.com/EasyEngine/dockerfiles.

• Updates for cron, MailHog, New Relic, PostFix, and Redis have to be done carefully as they might get bumped up to a new major version.
• Untag inactive maintainers from the Dockerfiles.
• Tag parent image to a specific version instead of latest.
• Maintain a changelog for configuration changes.
• Add following to New Relic .ini file newrelic.ini updates dockerfiles#109