Upgrade Django to resolve security vulnerabilities

[amplifi]

Current version: 1.9.6
Latest stable version: 1.10.2

Multiple vulns affecting v1.9, listed here: https://docs.djangoproject.com/en/1.10/releases/security/

Changelogs for upgrading from 1.9.6 to 1.10.2: https://docs.djangoproject.com/en/1.10/releases/

Note there are some backwards incompatible changes when coming from 1.9.x: https://docs.djangoproject.com/en/1.10/releases/1.10/#backwards-incompatible-1-10

[seav]

Resolving this issue should also resolve #537, though the latter should be confirmed to be fixed first before closing.

[oliverroick]

I opened a #887 to upgrade to Django 1.9.10, which has the necessary security fixes. Upgrading to 1.10 will take a bit longer, because of incompatible changes.