title: 'dict' object has no attribute 'pk' Django Rest API Framework
body: <p>Im using Django Rest API Framework, I want to upload multiple images for a single project using Angular js.</p>
  
  <p>Here's my model:</p>
  
  <pre><code>class Project(models.Model):
      created = models.DateTimeField(auto_now_add=True)
      updated = models.DateTimeField(auto_now=True)
      owner = models.ForeignKey(User)
      number_of_photos = models.IntegerField()
  
  class Photo(models.Model):
      created = models.DateTimeField(auto_now_add=True)
      updated = models.DateTimeField(auto_now=True)
      images = models.ImageField(upload_to='photos/', max_length=254)
      project = models.ForeignKey(Project)
  </code></pre>
  
  <p>I have this serializers:</p>
  
  <pre><code>class ProjectSerializer(serializers.ModelSerializer):
      class Meta:
          model = Project
          fields = ('id', 'created', 'number_of_photos', 'owner')
  
      def create(self, validated_data):
          project = Project.objects.create(**validated_data)
          return project
  
  class UploadSerializer(serializers.ModelSerializer):
      project = ProjectSerializer(many=True, read_only=True)
  
      class Meta:
          model = Photo
          fields = ('url', 'created', 'images', 'project')
  </code></pre>
  
  <p>In my view I got this inside my viewsets.ModelViewSet</p>
  
  <pre><code>serializer = UploadSerializer(data=photo_array, many=True, context={'request': request})
  
  if serializer.is_valid():
              serializer.save()
              return Response(serializer.data, status=status.HTTP_201_CREATED)
  </code></pre>
  
  <p>The variable <strong>photo_array</strong> contains:</p>
  
  <blockquote>
    <p>[{'project': u'1', 'images': {u'name': u'test-image.png', u'lastModifiedDate': u'2015-04-22T08:51:11.000Z', u'webkitRelativePath': u'', u'lastModified': 1429692671000, u'type': u'image/png', u'size': 43152}}, {'project': u'1', 'images': {u'name': u'test.png', u'lastModifiedDate': u'2015-04-08T08:35:17.000Z', u'webkitRelativePath': u'', u'lastModified': 1428482117000, u'type': u'image/png', u'size': 127433}}]</p>
  </blockquote>
  
  <p>But it gives me an error <strong>'dict' object has no attribute 'pk'</strong></p>
  
  <p>Did my photo_array variable cause this problem?.</p>