Bump django from 2.1.7 to 2.1.11

Bumps [django](https://github.com/django/django) from 2.1.7 to 2.1.11.
- [Release notes](https://github.com/django/django/releases)
- [Commits](django/django@2.1.7...2.1.11)

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

Author: dependabot[bot]

requirements.txt

@@ -1,4 +1,4 @@
-Django==2.1.7
+Django==2.1.11
 pkg-resources
 pycryptodome==3.8.0
 pytz==2018.9