Turn streaming request parsing back on for 1.3. Fix CSRF which was breaking it.…

Turn streaming request parsing back on for 1.3.  Fix CSRF which was breaking it.  It's really not at all obvious if we need to byte limit the stream that we hand over or not.

djangorestframework/request.py

@@ -68,6 +68,7 @@ class RequestMixin(object):
         if not hasattr(self, '_stream'):
             request = self.request
 
+            # Currently only supports parsing request body as a stream with 1.3
             if hasattr(request, 'read'):
                 # It's not at all clear if this needs to be byte limited or not.
                 # Maybe I'm just being dumb but it looks to me like there's some issues