Avoid globally polluting ::String class

lib/bullet/detector/unused_eager_loading.rb

@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+using Bullet::Ext::String
+
 module Bullet
   module Detector
     class UnusedEagerLoading < Association

lib/bullet/ext/string.rb

@@ -1,7 +1,13 @@
 # frozen_string_literal: true
 
-class String
-  def bullet_class_name
-    sub(/:[^:]*?$/, '')
+module Bullet
+  module Ext
+    module String
+      refine ::String do
+        def bullet_class_name
+          sub(/:[^:]*?$/, '')
+        end
+      end
+    end
   end
 end

lib/bullet/registry/object.rb

@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+using Bullet::Ext::String
+
 module Bullet
   module Registry
     class Object < Base

spec/bullet/ext/string_spec.rb

@@ -2,6 +2,8 @@
 
 require 'spec_helper'
 
+using Bullet::Ext::String
+
 describe String do
   context 'bullet_class_name' do
     it 'should only return class name' do