Fix bug in AR integration

[Fixes #789]

lib/paper_trail.rb

@@ -176,6 +176,10 @@ unless PaperTrail.active_record_protected_attributes?
   end
 end
 
+ActiveSupport.on_load(:active_record) do
+  include PaperTrail::Model
+end
+
 # Require frameworks
 require "paper_trail/frameworks/sinatra"
 if defined?(::Rails) && ActiveRecord::VERSION::STRING >= "3.2"

lib/paper_trail/frameworks/active_record.rb

@@ -2,7 +2,3 @@
 # since otherwise the model(s) will get loaded in via the `Rails::Engine`.
 require "paper_trail/frameworks/active_record/models/paper_trail/version_association"
 require "paper_trail/frameworks/active_record/models/paper_trail/version"
-
-ActiveSupport.on_load(:active_record) do
-  include PaperTrail::Model
-end

lib/paper_trail/frameworks/rails/engine.rb

@@ -5,7 +5,6 @@ module PaperTrail
       paths["app/models"] << "lib/paper_trail/frameworks/active_record/models"
       config.paper_trail = ActiveSupport::OrderedOptions.new
       initializer "paper_trail.initialisation" do |app|
-        ActiveRecord::Base.send :include, PaperTrail::Model
         PaperTrail.enabled = app.config.paper_trail.fetch(:enabled, true)
       end
     end