Include hieradata

https://github.gds/gds/puppet/pull/1060 adds support for Hiera to our Puppet.

Support for Hiera was added in Vagrant 1.2.3 so Hiera will not work if Vagrant version < 1.2.3.

This PR doesn't need to wait for the Puppet one, it one can be merged straight away. It won't fail for Vagrant < 1.2.3.