Bump django from 1.11.18 to 1.11.21

Bumps [django](https://github.com/django/django) from 1.11.18 to 1.11.21.
- [Release notes](https://github.com/django/django/releases)
- [Commits](django/django@1.11.18...1.11.21)

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

Author: dependabot[bot]

setup.py

@@ -18,7 +18,7 @@
     author='Deep Compute, LLC',
     author_email='contact@deepcompute.com',
     install_requires=[
-    'django==1.11.18',
+    'django==1.11.21',
     ],
     classifiers=[
         'Environment :: Web Environment',