Bump django from 1.11.24 to 1.11.28

Bumps [django](https://github.com/django/django) from 1.11.24 to 1.11.28.
- [Release notes](https://github.com/django/django/releases)
- [Commits](django/django@1.11.24...1.11.28)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements.txt

@@ -6,7 +6,7 @@ certifi==2019.11.28
 chardet==3.0.4
 coverage==5.0.4
 dj-database-url==0.5.0
-Django==1.11.24
+Django==1.11.28
 django-crispy-forms==1.9.0
 django-forms-bootstrap==3.1.0
 django-simple-history==2.8.0