Update configuration of Vagrant box.

Updating vbguest to the latest 3.6.10 seems to break shared mounts.

[CI skip]
Replace author/name separator from `/` to `-`.

I suppose it was just something I got wrong from the start; in any case, see
http://docs.puppetlabs.com/puppet/latest/reference/modules_publishing.html#a-note-on-module-names for an explanation.