Provide non regression feature test when ActiveRecord::Base is loaded

It happens if the AR::Base as already been loaded.

For example:
DatabaseCleaner/database_cleaner-active_record#91

features/initializers.feature

@@ -0,0 +1,15 @@
+Feature: properly integrate with Rails and other gems
+
+  Background:
+    When I create a new rails application
+    And I add "factory_bot_rails" from this project as a dependency
+    And I run `bundle install` with a clean environment
+
+  Scenario: handle already loaded ActiveRecord::Base by another gems earlier
+    When I run the following commands:
+      """bash
+      cat config/application.rb
+      sed -i -e '/require "rails\/test_unit\/railtie"/a\'$'\n''require "active_record/base"' config/application.rb
+      """
+    When I run `bundle exec rake test` with a clean environment
+    Then the output should contain "0 runs"