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

@@ -1,5 +1,5 @@
 autopep8==1.5
-Django==1.11.24
+Django==1.11.28
 django-forms-bootstrap==3.1.0
 pycodestyle==2.5.0
 pytz==2019.3