Version 2.2: Ubuntu 14.04, Django 1.7.1

As it says:

- Ubuntu 14.04
- Django 1.7.1
- Postgres 9.3

Also python package version bumps:

- psycopg2 2.4.6 -> 2.5.4
- django-devserver 0.5.0 -> 0.8.0
- django-compressor 1.3 -> 1.4
- django-debug-toolbar 0.9.4 -> 1.2.2
- Pillow 2.0.0 -> 2.6.1
- fabric 1.6.1 -> 1.10.0
- gunicorn 0.17.4 -> 19.1.1
- removal of South

Also added zeroing of empty space on the box before packaging, which saved around 130 MiB.

I haven't specifically checked documentation for known version incompatibilities here, but this built itself and vagrant-django-template (there's a pull request there too) happily set up for me using this box.

I have assumed a version number bump to 2.2.