Django Box 2.0 Released (Vagrant virtual machine for testing Django)

[Josh Smeaton]

I've pushed an update to the django-box project (https://github.com/django/django-box) to bring the environment up to compatibility with Django 2.0. If you don't know what django-box is, it's a virtualbox virtual machine with a Vagrant file, providing all (most) dependencies required to run the Django test suite on all supported databases (except Oracle). It's based on a very similar setup to djangoci.com Jenkins instances, which means tests that pass locally within the image are likely to pass on CI, reducing feedback time.

Rather than updating the existing box from 1.11 to 2.0, I've created a new release, which will allow us to backport necessary changes to the 1.11 release.

The best way to use this project is to clone it beside your Django checkout, and run `vagrant up` from there. The docs do go through how to download the virtualbox image without going through vagrant if you'd prefer to install the image that way.

Major changes:

- Added python 3.6

- Updated Vagrant version to 1.9.1 (Readme)

- Updated VirtualBox version to 5.1.14 (Readme)

- Pinned tox to version 2.3

I specifically did *not* remove python 2.7, so that you can continue to run tests on a Django 1.11 checkout even with this version of the image.