Bump django from 1.11.21 to 1.11.22

Bumps [django](https://github.com/django/django) from 1.11.21 to 1.11.22.
- [Release notes](https://github.com/django/django/releases)
- [Commits](https://github.com/django/django/commits)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

requirements.txt

@@ -1,5 +1,5 @@
 coverage==4.5.3
-Django==1.11.21 # pyup: <2.0
+Django==1.11.22 # pyup: <2.0
 django-debug-toolbar==2.0
 docutils==0.14
 freezegun==0.3.12