Fix and improve broken install script.

It wouldn't work at all, because it wasn't using a virtualenv and e.g.
on Ubuntu precise you'll only get Django 1.3 that way. Now, use the
separate post deploy script that now exists, and run gunicorn using the
virtualenv's python. Don't install compass, it isn't needed; update the
example config files; add more output.
Travis working somewhat; it's using PostGIS 2.1.

Travis already has PostGIS installed. This means Django 1.4 will fail,
it only got proper support for PostGIS 2 with 1.5.