build(deps): bump django from 1.11.29 to 2.2.28

Bumps [django](https://github.com/django/django) from 1.11.29 to 2.2.28.
- [Release notes](https://github.com/django/django/releases)
- [Commits](django/django@1.11.29...2.2.28)

---
updated-dependencies:
- dependency-name: django
  dependency-type: direct:production
...

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

Author: dependabot[bot]

requirements.txt

@@ -6,7 +6,7 @@ certifi==2017.11.5
 chardet==3.0.4
 coverage==4.5.1
 dj-database-url==0.4.2
-Django==1.11.29
+Django==2.2.28
 django-appconf==1.0.2
 django-bootstrap3==9.1.0
 django-braces==1.11.0