title: Django REST Framework tutorial gives error, don't understand why
body: <p>I am working through the <a href="http://www.django-rest-framework.org/tutorial/1-serialization/" rel="nofollow">full tutorial</a> in the <a href="http://www.django-rest-framework.org/" rel="nofollow">Django REST Framework website</a> and am getting an error that doesn't make sense to me.</p>
  
  <p>Here's the python session:</p>
  
  <pre><code>&gt;&gt;&gt; from snippets.models import Snippet
  &gt;&gt;&gt; from snippets.serializers import SnippetSerializer
  &gt;&gt;&gt; from rest_framework.renderers import JSONRenderer
  &gt;&gt;&gt; from rest_framework.parsers import JSONParser
  &gt;&gt;&gt; snippet = Snippet(code='foo = "bar"\n')
  &gt;&gt;&gt; snippet.save()
  &gt;&gt;&gt; snippet = Snippet(code='print "hello, world"\n')
  &gt;&gt;&gt; snippet.save()
  &gt;&gt;&gt; serializer = SnippetSerializer(snippet)
  &gt;&gt;&gt; serializer.data
  ReturnDict([('pk', 3), ('title', u''), ('code', u'print "hello, world"\n'), ('linenos', False), ('language', 'python'), ('style', 'friendly')])
  &gt;&gt;&gt; content = JSONRenderer().render(serializer.data)
  &gt;&gt;&gt; content
  '{"pk":3,"title":"","code":"print \\"hello, world\\"\\n","linenos":false,"language":"python","style":"friendly"}'
  &gt;&gt;&gt; from rest_framework.compat import BytesIO
  &gt;&gt;&gt; stream = BytesIO(content)
  &gt;&gt;&gt; data = JSONParser().parse(stream)
  &gt;&gt;&gt; serializer = SnippetSerializer(data=data)
  &gt;&gt;&gt; serializer.is_valid()
  False
  &gt;&gt;&gt; serializer.errors
  ReturnDict([('title', [u'This field may not be blank.'])])
  &gt;&gt;&gt; 
  </code></pre>
  
  <p>Here's the relevant line from the serializer:</p>
  
  <pre><code>title = serializers.CharField(
      required=False,
      max_length=100,
      )
  </code></pre>
  
  <p>... and the relevant line from the model:</p>
  
  <pre><code>title = models.CharField(max_length=100, blank=True, default='')
  </code></pre>
  
  <p>The model and the serializer both allow empty values for 'title', but the error indicates that an empty value is not valid. Can someone explain why I might be seeing this?</p>