Update django to 2.0.4

[pyup-bot]

This PR updates Django from 2.0.3 to 2.0.4.

Changelog

2.0.4

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

*April 2, 2018*

Django 2.0.4 fixes several bugs in 2.0.3.

Bugfixes
========

* Fixed a crash when filtering with an ``Exists()`` annotation of a queryset
containing a single field (:ticket:`29195`).

* Fixed admin autocomplete widget's translations for `zh-hans` and `zh-hant`
languages (:ticket:`29213`).

* Corrected admin's autocomplete widget to add a space after custom classes
(:ticket:`29221`).

* Fixed ``PasswordResetConfirmView`` crash when using a user model with a
``UUIDField`` primary key and the reset URL contains an encoded primary key
value that decodes to an invalid UUID (:ticket:`29206`).

* Fixed a regression in Django 1.11.8 where combining two annotated
``values_list()`` querysets with ``union()``, ``difference()``, or
``intersection()`` crashed due to mismatching columns (:ticket:`29229`).

* Fixed a regression in Django 1.11 where an empty choice could be initially
selected for the ``SelectMultiple`` and ``CheckboxSelectMultiple`` widgets
(:ticket:`29273`).

* Fixed a regression in Django 2.0 where ``OpenLayersWidget`` deserialization
ignored the widget map's SRID and assumed 4326 (WGS84) (:ticket:`29116`).


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

Links

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

[coveralls]

Coverage remained the same at 87.846% when pulling 27584dd on pyup-update-django-2.0.3-to-2.0.4 into 567f1e1 on master.