[#54693536] Update basebox images

Includes Puppet 3.4 installed from a Debian package: alphagov/boxes#4

This will be downloaded automatically the next time someone brings up a box
(`vagrant up`) from fresh (clean install or after `vagrant destroy`).
Merge pull request #21 from alphagov/54693536-vagrant_vbox_puppet_34_deb

[#54693536] Update basebox images