Add Vagrantfile and a bootstrap file for provisioning redis

This allows running tests in a virtual machine so you avoid any risk of clobbering your existing Redis database. It uses [Vagrant][1] to set up the VM.

You should be able to use it with something along the line of the following:

1. Install VirtualBox and Vagrant
2. `vagrant up`
3. `vagrant ssh`
4. `cd /vagrant`
5. `nosetests`

  [1]: http://www.vagrantup.com/