TemplateDoesNotExist is a private function that should never be used.
In Django 1.9, upstream authors decided to move it to another path.
This patch defines TemplateDoesNotExist directly in jingo instead of
using the internal Django version.

This patch adds a call to django.setup() which is now needed in Django.

Django 1.9 removed django.utils.six. Jingo then should use six
directly, not from Django.

In Django 1.10, django.template.loader.BaseLoader is removed completely.
This patch uses django.template.loaders.base.Loader instead.

In Django 1.10, we need to add this to INSTALLED_APPS:
    django.contrib.sites
    django.contrib.contenttypes
    django.contrib.auth

Without this, unit tests are failing over with not-found templates.

In Django 1.10, many things which were previously declared separatly
now have to go in a TEMPLATES = [] object.

In Django 1.10, settings.TEMPLATE_DEBUG. Instead, we should use
settings.TEMPLATES[0]['OPTIONS']['debug'].

In Django 1.10, django.forms.util was renamed django.forms.utils
(deprecation cycle ended, and there's no fallback).

In Django 1.10, the __init__() method of the Loader class takes
2 args, not 1 anymore. This patch fixes that.

In Django 1.10, django.conf.urls.patterns (and its associated function)
doesn't exist anymore, and we *must* use url(), not just () for the
urlpatterns tuples.

django.template.loaders.base doesn't exist in Django 1.7. This patch
makes the Django 1.10 to continue to work with older version.

Previous commit uses six, not from Django. This patch adds six
as runtime requires.

Previous commit added a 2nd param for the __init__ of the Loader
class. However, this broke compat with older version of Django.
This patch solves that by making this 2nd parameter optional.