chore(dependencies): Bump Django from 1.11.7 to 2.0

Bumps [Django](https://www.djangoproject.com/) from 1.11.7 to 2.0.

Author: dependabot[bot]

requirements.txt

@@ -7,7 +7,7 @@ chardet==3.0.4
 cryptography==2.1.4
 defusedxml==0.5.0
 dj-database-url==0.4.2
-Django==1.11.7
+Django==2.0
 django-security==0.9.5
 django-webpack-loader==0.5.0
 flake8==3.5.0