enable redis cache store

This updates production and the development environment to actually make
use of the Redis cache store.  Production adds the cache store config,
while development transitions from using the in-memory store over to the
external redis config.

config/environments/development.rb

@@ -23,7 +23,8 @@
     config.action_controller.perform_caching = true
     config.action_controller.enable_fragment_cache_logging = true
 
-    config.cache_store = :memory_store
+    # config.cache_store = :memory_store
+    config.cache_store = :redis_cache_store, {URL: ENV.fetch("REDIS_URL", "redis://localhost:6397/1")}
     config.public_file_server.headers = {
       "Cache-Control" => "public, max-age=#{2.days.to_i}"
     }

config/environments/production.rb

@@ -54,6 +54,7 @@
 
   # Use a different cache store in production.
   # config.cache_store = :mem_cache_store
+  config.cache_store = :redis_cache_store, {URL: ENV.fetch("REDIS_URL", "redis://localhost:6397/1")}
 
   # Use a real queuing backend for Active Job (and separate queues per environment).
   # config.active_job.queue_adapter     = :resque