Fix elasticache setup in SaltStack orchestration

[ryan-lane]

For the autoscale group to launch correctly, it's necessary to know the elasticache IP address in the cloud-init.

One option here is to add a call in the cloud-init that looks up the elasticache IP address and injects it as an environment variable. Another (likely better option) is to fix issue #12, which would let us remove elasticache completely.

[ryan-lane]

Since we dropped the redis requirement in ab8bc60 it doesn't make any sense to make this work for the orchestration. We can just remove elasticache from it.