Use vagrant-cachier with Virtualbox
Use vagrant-cachier with Virtualbox

Unfortunately doesn't work well with VMWare, so not enabling for all
environments just yet.

See https://github.com/fgrehm/vagrant-cachier/issues/24
alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet