Redis support
Summary
Currently workers on GitLab are orchestrated and controlled via RabbitMQ due to the choice of celery. While this works, RabbitMQ is a resource hogger. RabbitMQ uses an insane amount of resources for something that should just pass around messages. There has been cases where nomoya (the production server) ran out of resources because RabbitMQ hogs them all.
Other projects such as Sentry which also uses Django and celery, uses Redis. From the experience of self-hosting Sentry for GitMate, redis is more controlled and doesn't waste resources.
Proposal
Add support for Redis.