Update django to 2.0.6

[pyup-bot]

This PR updates Django from 2.0.4 to 2.0.6.

Changelog

2.0.6

==========================

*June 1, 2018*

Django 2.0.6 fixes several bugs in 2.0.5.

Bugfixes
========

* Fixed a regression that broke custom template filters that use decorators
(:ticket:`29400`).

* Fixed detection of custom URL converters in included patterns
(:ticket:`29415`).

* Fixed a regression that added an unnecessary subquery to the ``GROUP BY``
clause on MySQL when using a ``RawSQL`` annotation (:ticket:`29416`).

* Fixed ``WKBWriter.write()`` and ``write_hex()`` for empty polygons on
GEOS 3.6.1+ (:ticket:`29460`).

* Fixed a regression in Django 1.10 that could result in large memory usage
when making edits using ``ModelAdmin.list_editable`` (:ticket:`28462`).


==========================

2.0.5

==========================

*May 1, 2018*

Django 2.0.5 fixes several bugs in 2.0.4.

Bugfixes
========

* Corrected the import paths that ``inspectdb`` generates for
``django.contrib.postgres`` fields (:ticket:`29307`).

* Fixed a regression in Django 1.11.8 where altering a field with a unique
constraint may drop and rebuild more foreign keys than necessary
(:ticket:`29193`).

* Fixed crashes in ``django.contrib.admindocs`` when a view is a callable
object, such as ``django.contrib.syndication.views.Feed`` (:ticket:`29296`).

* Fixed a regression in Django 1.11.12 where ``QuerySet.values()`` or
``values_list()`` after combining an annotated and unannotated queryset with
``union()``, ``difference()``, or ``intersection()`` crashed due to mismatching
columns (:ticket:`29286`).


==========================

Links

• PyPI: https://pypi.org/project/django
• Changelog: https://pyup.io/changelogs/django/
• Homepage: https://www.djangoproject.com/

[pyup-bot]

Closing this in favor of #19