Updates with no operator should default to $set Fix #667
Allowed failures for Django development version.
Python 2.6 requires positioning by number of fragments in format.

This commit will restore Python 2.6 compatability.
Fix for post_init signal to receive correct state of _created flag.
Fix setting of _created flag in base.Document constructor
Add testcase
Update querying.rst
Merge pull request #635 from SergeChmelev/master

Fix for post_init signal to receive correct state of _created flag.
Merge pull request #692 from rochacbruno/master

Updates with no operator should default to $set Fix #667
Added @rochacbrun to the AUTHORS file. #692
Follow ReferenceFields in EmbeddedDocuments with select_related

For the following structure:

    class Playlist(Document):
        items = ListField(EmbeddedDocumentField("PlaylistItem"))

    class PlaylistItem(EmbeddedDocument):
        song = ReferenceField("Song")

    class Song(Document):
        title = StringField()

this patch prevents the N+1 queries otherwise required to fetch all
the `Song` instances referenced by all the `PlaylistItem`s.