Only start application level processes via foreman

This pull request removes `redis-server` from the `Procfile`.

Starting `redis-server` via foreman when it's already running will cause foreman start to fail. Having redis already running is pretty common for a developer machine.

It seems foreman is meant for managing application level processes, not system level processes. Note that the Procfile already doesn't include management for the symmetric postgresql process(es).

If you'd like to not think about having redis-server running, it's better to use existing OS level tooling to manage it.

**e.g** on OSX via homebrew `ln -sfv /usr/local/opt/redis/*.plist ~/Library/LaunchAgents`