Update django-treebeard to 4.3.1

[pyup-bot]

This PR updates django-treebeard from 4.3 to 4.3.1.

Changelog

4.3.1

----------------------------

* Added check to avoid unnecessary database query for ``MP_Node.get_ancestors()``
if the node is a root node.
* Drop support for Python-3.4.
* Play more nicely with other form classes, that implement ``__init__(self, *args, **kwargs)``,
e.g. django-parler's ``TranslatableModelForm``, where `kwargs.get('instance')` is ``None``
when called from here.
* Sorting on path on necessary queries, fixes some issues and stabilizes the whole MP section.
* Add German translation strings.

Links

• PyPI: https://pypi.org/project/django-treebeard
• Changelog: https://pyup.io/changelogs/django-treebeard/
• Repo: https://github.com/django-treebeard/django-treebeard/

[coveralls]

Coverage remained the same at 87.803% when pulling abb35d6 on pyup-update-django-treebeard-4.3-to-4.3.1 into baaf67e on master.