Remove memcache from production config

I don't know enough about our caching situation to know where memcache performs meaningfully better than Rails's in-memory cache. Let's delete it for now and see if there's a problem, to simplify the deploy environment!

Gemfile

@@ -69,11 +69,6 @@ group :development do
   gem 'rvm-capistrano', '~> 1.5.6', require: false
 end
 
-# For production caching.
-group :production do
-  gem 'memcache-client', '~> 1.8.5', :require => 'memcache'
-end
-
 # For testing.
 group :test do
   gem 'factory_girl_rails', '~> 4.9'

Gemfile.lock

@@ -165,7 +165,6 @@ GEM
       net-pop
       net-smtp
     marcel (1.0.2)
-    memcache-client (1.8.5)
     method_source (1.0.0)
     mime-types (3.4.1)
       mime-types-data (~> 3.2015)
@@ -334,7 +333,6 @@ DEPENDENCIES
   http_accept_language (~> 2.1, >= 2.1.1)
   jsbundling-rails (~> 1.1)
   letter_opener (~> 1.8, >= 1.8.1)
-  memcache-client (~> 1.8.5)
   mysql2 (~> 0.5.5)
   nokogiri (~> 1.15, >= 1.15.3)
   parallel (~> 1.23)

config/environments/production.rb

@@ -32,7 +32,7 @@ Rails.application.configure do
   # config.logger = SyslogLogger.new
 
   # Use a different cache store in production
-  config.cache_store = :mem_cache_store, { namespace: "openneo-impress-rails" }
+  # config.cache_store = :mem_cache_store, { namespace: "openneo-impress-rails" }
 
   # Disable Rails's static asset server
   # In production, Apache or nginx will already do this