Fixed
- Previously, albums with multiple media types would always have photos first,
then video files, and then audio files, regardless of the values of the
`ordering` and `name` columns. Now it is possible for the media types to
appear in any order.
- Added the `on_delete` argument to the foreign keys to fix a Django 1.10
warning. For more information, see
[the "ForeignKey and OneToOneField on_delete argument" section](https://docs.djangoproject.com/en/dev/releases/1.9/foreignkey-and-onetoonefield-on-delete-argument)
of the Django 1.9 release notes.