[STORE] Fixed, that MyModel#save does in fact persist updated_at attribute

Without this patch, a persistence model will not actually save the updated_at timestamp to Elasticsearch.

Closes elastic#389
Closes elastic#342

Author: ryansch

elasticsearch-persistence/lib/elasticsearch/persistence/model.rb

@@ -121,8 +121,8 @@ def deserialize(document)
 
           # Set up common attributes
           #
-          attribute :created_at, DateTime, default: lambda { |o,a| Time.now.utc }
-          attribute :updated_at, DateTime, default: lambda { |o,a| Time.now.utc }
+          attribute :created_at, Time, default: lambda { |o,a| Time.now.utc }
+          attribute :updated_at, Time, default: lambda { |o,a| Time.now.utc }
 
           attr_reader :hit
         end

elasticsearch-persistence/lib/elasticsearch/persistence/model/store.rb

@@ -53,10 +53,10 @@ def save(options={})
               options.update index: self._index if self._index
               options.update type:  self._type  if self._type
 
-              response = self.class.gateway.save(self, options)
-
               self[:updated_at] = Time.now.utc
 
+              response = self.class.gateway.save(self, options)
+
               @_id       = response['_id']
               @_index    = response['_index']
               @_type     = response['_type']

elasticsearch-persistence/test/integration/model/model_basic_test.rb

@@ -135,7 +135,7 @@ class ::Person
           person = Person.create name: 'John Smith'
           updated_at = person.updated_at
 
-          sleep 1
+          sleep 0.25
           person.touch
 
           assert person.updated_at > updated_at, [person.updated_at, updated_at].inspect
@@ -144,6 +144,20 @@ class ::Person
           assert found.updated_at > updated_at, [found.updated_at, updated_at].inspect
         end
 
+        should 'update the object timestamp on save' do
+          person = Person.create name: 'John Smith'
+          person.admin = true
+          sleep 0.25
+          person.save
+
+          Person.gateway.refresh_index!
+
+          found = Person.find(person.id)
+
+          # Compare without milliseconds
+          assert_equal person.updated_at.to_i, found.updated_at.to_i
+        end
+
         should "respect the version" do
           person = Person.create name: 'John Smith'