Set up Redis server to run in containers

As discussed about a month ago, I'd love for donate-neo to have access to a locally-running Redis server.

It looks like I missed a reasonable question about this in IRC - my apologies for only seeing it now, when looking up our original discussion about this ask - namely, "what would we need a Redis server for?" There are actually several places in the donate-neo codebase where a Redis server will need to be leveraged in the imminent future:

1. Communication with CiviCRM via shared-queue Resque messaging (we only use the API to retrieve perk and YEC data)
2. Rate-limiting by IP
3. Newsletter signup token generation
4. Django-level caching for performance
5. Unit testing for the above

As such, donate-neo containers we deploy should install and run redis-server before the Django server is itself spun up. Happy to chat further about any of the above.