Use Railtie to initialize active support

lib/css_splitter.rb

@@ -1,4 +1,8 @@
-require "css_splitter/engine"  if defined?(Rails)
+if defined? Rails
+  require 'css_splitter/railtie'
+  require 'css_splitter/engine'
+end
+
 require "css_splitter/sprockets_engine"
 require "css_splitter/splitter"
 

lib/css_splitter/engine.rb

@@ -1,15 +1,5 @@
 module CssSplitter
   class Engine < ::Rails::Engine
     isolate_namespace CssSplitter
-
-    initializer 'css_splitter.sprockets_engine', after: 'sprockets.environment', group: :all do |app|
-      app.assets.register_bundle_processor 'text/css', CssSplitter::SprocketsEngine
-    end
-
-    initializer 'css_splitter.action_controller' do |app|
-      ActiveSupport.on_load :action_controller do
-        helper CssSplitter::ApplicationHelper
-      end
-    end
   end
 end

lib/css_splitter/railtie.rb

@@ -0,0 +1,13 @@
+module CssSplitter
+  class Railtie < ::Rails::Railtie
+    initializer 'css_splitter.sprockets_engine', after: 'sprockets.environment', group: :all do |app|
+      app.assets.register_bundle_processor 'text/css', CssSplitter::SprocketsEngine
+    end
+
+    initializer 'css_splitter.action_controller' do |app|
+      ActiveSupport.on_load :action_controller do
+        helper CssSplitter::ApplicationHelper
+      end
+    end
+  end
+end