[MODEL] Fixed records sorting with ActiveRecord 5.x

Closes elastic#618

Author: Savater Sebastien

elasticsearch-model/lib/elasticsearch/model/adapters/active_record.rb

@@ -26,7 +26,10 @@ def records
             # by redefining `to_a`, unless the user has called `order()`
             #
             sql_records.instance_exec(response.response['hits']['hits']) do |hits|
-              define_singleton_method :to_a do
+              ar_records_method_name = :to_a
+              ar_records_method_name = :records if defined?(::ActiveRecord) && ::ActiveRecord::VERSION::MAJOR >= 5
+
+              define_singleton_method(ar_records_method_name) do
                 if defined?(::ActiveRecord) && ::ActiveRecord::VERSION::MAJOR >= 4
                   self.load
                 else

elasticsearch-model/test/integration/active_record_basic_test.rb

@@ -104,7 +104,10 @@ def as_indexed_json(options = {})
         end
 
         should "preserve the search results order for records" do
-          response = Article.search('title:code')
+          response = Article.search query: { match: { title: 'code' }}, sort: { clicks: :desc }
+
+          assert_equal response.records[0].clicks, 3
+          assert_equal response.records[1].clicks, 2
 
           response.records.each_with_hit do |r, h|
             assert_equal h._id, r.id.to_s