Update link to Django documentation in urls.py.

As per requirements.txt we are using Django version 1.10. It makes sense
to link to the documentation for that version as well.
Also, the documentation for the previous version has a notice on the top
that informs about the version being unsafe which is a bit disconcerting
when seeing it.

src/paperless/urls.py

@@ -1,7 +1,7 @@
 """paperless URL Configuration
 
 The `urlpatterns` list routes URLs to views. For more information please see:
-    https://docs.djangoproject.com/en/1.9/topics/http/urls/
+    https://docs.djangoproject.com/en/1.10/topics/http/urls/
 Examples:
 Function views
     1. Add an import:  from my_app import views