Add redis to procfile

This is useful for general running i.e. not debugging
specific errors.  foreman seems to truncate logs from the
web server and does not play nicely with pry.  But, for
general day-to-day running this can be useful

Procfile

@@ -1,2 +1,3 @@
 web: bundle exec puma -C config/puma.rb
 worker: bundle exec sidekiq
+redis: redis-server