Add vagrant config.

Added Vagrantfile and simple provisioning script. This sets up the
packages, gems and databases so that `rake db:migrate` is ready to
run. This might be too much and perhaps more should be done by the
user themselves, I'm not sure...
Move vagrant provisioning script to a better location.
Merge remote-tracking branch 'upstream/master' into vagrant
Added some docs for Vagrant usage.

It doesn't currently recomment using Vagrant - there are probably
some bugs to work out in the process before we can do that.
Migrate the database on `vagrant up`.

Also fix the provisioning script so that it runs correctly when
the VM is upped, regardless of whether it's a clean install or
an 'up' of a previously halted VM.
Add some additional information to help people starting out on the project using vagrant, especially if you haven't used vagrant before.