Move caching initialization to Railtie

Also
- Add reference to config from ActiveModelSerializers.config
- correctly call super in FragmentCacheTest#setup
- rename test rails app from Foo to ActiveModelSerializers::RailsApplication

test/adapter/fragment_cache_test.rb

@@ -4,6 +4,7 @@ module ActiveModel
     module Adapter
       class FragmentCacheTest < Minitest::Test
         def setup
+          super
           @spam            = Spam::UnrelatedLink.new(id: 'spam-id-1')
           @author          = Author.new(name: 'Joao M. D. Moura')
           @role            = Role.new(name: 'Great Author', description: nil)

test/support/rails_app.rb

@@ -1,14 +1,18 @@
-class Foo < Rails::Application
+class ActiveModelSerializers::RailsApplication < Rails::Application
   if Rails::VERSION::MAJOR >= 4
     config.eager_load = false
+
     config.secret_key_base = 'abc123'
-    config.action_controller.perform_caching = true
+
     config.active_support.test_order = :random
+
     config.logger = Logger.new(nil)
+
+    config.action_controller.perform_caching = true
     ActionController::Base.cache_store = :memory_store
   end
 end
-Foo.initialize!
+ActiveModelSerializers::RailsApplication.initialize!
 
 module TestHelper
   Routes = ActionDispatch::Routing::RouteSet.new