Tutorial vagrant 273

Fixes #273 

Mostly just a copy of our top-level Vagrantfile - with some edits.  Clearly this suggests some maintenance issues.  Also note the caveat at the top of the new file about the required version of vagrant.  This isn't the optimal place for this warning but it's more or less the only reasonable place for now.  There's also no actual tutorial material included with this change - just a Vagrantfile that someone could probably use as part of a tutorial.

That's what #306 is.