Cleanerversion

- Starting with this version of CleanerVersion, Django versions < 1.8 are not supported anymore
- Support for UUID fields -> **Read the upgrade notes** ([here](http://cleanerversion.readthedocs.io/en/latest/doc/historization_with_cleanerversion.htmlcleanerversion-1-6-0-django-1-8-3)) regarding this CleanerVersion release!!
- Bugfix: Avoid overlapping versions upon version restore
- Bugfix: prefetch_related with historic versions of reverse FK objects
- PLUS: we're going stable starting with this version! :)

This release includes mainly bugfixes in the Admin interface (see PRs 106, 109, credits to dunkelstern) and in the behaviour when working with Many-to-Many-relationships to self (see PR 112, credits to brki).
You'll also notice a change that allows usage of Versionable objects that is closer to the Django default behaviour, by using objects as filter lookup values (see PR 113 for details, credits to brki).

This release extends the integration of CleanerVersion to Django's Admin interface.
Also, there are numerous fixes, like:
- reverse foreign key clearing now triggers a clone on related objects
- heterogeneous models (versioned and non-versioned ones) are now less error-prone

Check database for latest version when restoring a version

Added necessary files to CleanerVersion package;
Slightly updated the docs;

This latest minor release is backward compatible and adds the following features:
- Compatibility with Django 1.8 (LTS); additionally to Django 1.6 and Django 1.7 support has been extended to Django's latest release
- Integration to Django's Admin interface; It is now possible to manage your versions, display an object's history and to filter objects at a given point in time. Credits go to boydjohnson and peterfarrell.
- Bugfixes