Log Message:
Changes 1.8.4:
* Denial-of-service possibility in logout() view by filling session store.
* Bugfixes:
- Added the ability to serialize values from the newly added UUIDField.
- Added a system check warning if the old TEMPLATE_* settings are defined in \ 
addition to the new TEMPLATES setting.
- Fixed QuerySet.raw() so InvalidQuery is not raised when using the db_column \ 
name of a ForeignKey field with primary_key=True.
- Prevented an exception in TestCase.setUpTestData() from leaking the transaction.
- Fixed has_changed() method in contrib.postgres.forms.HStoreField.
- Fixed the recording of squashed migrations when running the migrate command.
- Moved the unsaved model instance assignment data loss check to Model.save() to \ 
allow easier usage of in-memory models.
- Prevented varchar_patterns_ops and text_patterns_ops indexes for ArrayField.