This is a TODO file for only this branch (config-overhaul)

* Config validation
* What happens if a configured box doesn't exist?
* Separation of global vs VM configuration.
* Put VM-specific config directly into Vagrant::VM objects
* Only allow one kind of vagrantfile to be loaded (i.e. if both
  Vagrantfile and vagrantfile exist, throw an error)
* Nicer error if can't setup home directory
* vagrant box add should error if box already exists
* Default name to folder name + timestamp