Dead installation link in vagrant documentation
If you click on `installation in
or
(Step 5) https://gitlab.com/gitlab-org/gitlab-development-kit/blob/master/doc/vagrant.md#vagrant-with-docker
the link leads to nowhere. I think it should go to https://gitlab.com/gitlab-org/gitlab-development-kit/blob/master/doc/set-up-gdk.md but I'm not certain