website/docs: link to real vagrant cloud url

This is mostly for cookies and google. If you're logged in to
www, you won't be logged in to apex, and visa versa. Also a Vagrant
Cloud bug but wanted to make it consistent on this end.

![cookies](https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcTKt-3ayAFFzjEXjwy3Q-3WjfdIrDxgTZ2chgmqZeBPi81mLSC65Q)