Add Vagrantfile for Vagrant VMs

If you have Vagrant installed, you can go to the vagrant directory and run
Vagrant commands like 'vagrant up' to manage a dev server VM.
Modify fabfile.py and add templates for dev server configuration

No longer depends on django-fab-deploy.  Uses only 2 templates
(local_settings.py and apache2_vhost.conf).  Limited functionality (dev
servers via Vagrant only); should be merged with earlier Fabric deployment
capability in the future.
Modify esp.wsgi to support Vagrant

On a Vagrant dev server, the virtualenv is in a non-standard location.
Add some code to detect this and adjust the path accordingly.
Update make_virtualenv.sh to support different directory locations

On Vagrant, you can't create a virtualenv within the working copy (at
least within the current design, which uses a shared folder for
convenience).  So, allow make_virtualenv.sh to accept the virtualenv path
as an argument (if there is no argument, it uses the normal location).
Also allow a --virtualenv option to be supplied to update_deps.sh which
passes it along.
Add initial documentation for Vagrant/Fabric deployment