Remove ActiveRecord patch

Patching ActiveRecord is dangerous. Furthermore, query optimization is
out of scope of this gem.
This fixes Travis builds for Rails 4.0 and 4.1.

lib/rails-settings/setting_object.rb

@@ -76,18 +76,5 @@ def _set_value(name, v)
     def _target_class
       target_type.constantize
     end
-
-    # Patch ActiveRecord to save serialized attributes only if they are changed
-    if ActiveRecord::VERSION::MAJOR < 4
-      # https://github.com/rails/rails/blob/3-2-stable/activerecord/lib/active_record/attribute_methods/dirty.rb#L70
-      def update(*)
-        super(changed) if changed?
-      end
-    else
-      # https://github.com/rails/rails/blob/4-0-stable/activerecord/lib/active_record/attribute_methods/dirty.rb#L73
-      def update_record(*)
-        super(keys_for_partial_write) if changed?
-      end
-    end
   end
 end

spec/queries_spec.rb

@@ -97,12 +97,5 @@
         user.settings(:dashboard).update_attributes! :foo => 'bar'
       }.to perform_queries(1)
     end
-
-    it "should not touch database if there are no changes made" do
-      expect {
-        user.settings(:dashboard).update_attributes :theme => 'pink'
-        user.settings(:calendar).update_attributes :scope => 'all'
-      }.to perform_queries(0)
-    end
   end
 end