[MODEL] Add type and id methods to Response::Result to prevent errors with Hashie::Mash

Since Hashie::Mash explicitely [defines](https://github.com/intridea/hashie/blob/953edec/lib/hashie/mash.rb#L75-L81)
`id` and `type` methods, the method_missing couldn't kick in.

The `id` and `type` attributes should be referenced from the attributes hash directly,
ie. from the main `_id` and `_type` properties, and not from `_source`.

Closes elastic#90

Author: berislavbabic

elasticsearch-model/lib/elasticsearch/model/response/result.rb

@@ -17,12 +17,30 @@ def initialize(attributes={})
           @result = Hashie::Mash.new(attributes)
         end
 
+        # Alias `id` to `_id`
+        #
+        def id
+          @result['_id']
+        end
+
+        # Alias `type` to `_type`
+        #
+        def type
+          @result['_type']
+        end
+
         # Delegate methods to `@result` or `@result._source`
         #
         def method_missing(name, *arguments)
           case
           when name.to_s.end_with?('?')
             @result.__send__(name, *arguments) || ( @result._source && @result._source.__send__(name, *arguments) )
+          when name.to_s == "id"
+            if @result._source && @result._source.respond_to?(name)
+              @result._source.__send__ name, *arguments
+            else
+              super
+            end
           when @result.respond_to?(name)
             @result.__send__ name, *arguments
           when @result._source && @result._source.respond_to?(name)

elasticsearch-model/test/integration/active_record_basic_test.rb

@@ -72,6 +72,13 @@ class ::Article < ActiveRecord::Base
           assert_equal [1, 2],     response.records.map(&:id)
         end
 
+        should "iterate aliased id and type over results" do
+          response = Article.search('title:test')
+
+          assert_equal ['1', '2'],             response.results.map(&:id)
+          assert_equal ['article', 'article'], response.results.map(&:type)
+        end
+
         should "access results from records" do
           response = Article.search('title:test')
 

elasticsearch-model/test/unit/response_result_test.rb

@@ -73,5 +73,16 @@ class Elasticsearch::Model::ResultTest < Test::Unit::TestCase
       result.as_json(except: 'foo')
     end
 
+    should "map the _id column to id" do
+      result = Elasticsearch::Model::Response::Result.new foo: 'bar', _id: 42
+
+      assert_equal 42, result.id
+    end
+
+    should "map the _type column to type" do
+      result = Elasticsearch::Model::Response::Result.new foo: 'bar', _type: 'baz'
+
+      assert_equal 'baz', result.type
+    end
   end
 end