Upgrade vm.box_version to 2 and beyond

Vagrantfile

@@ -13,7 +13,7 @@ Vagrant.configure(2) do |config|
   # Every Vagrant development environment requires a box. You can search for
   # boxes at https://atlas.hashicorp.com/search.
   config.vm.box = "torchbox/wagtail-jessie64"
-  config.vm.box_version = "~> 1.0"
+  config.vm.box_version = "~> 2.0"
 
   # Disable automatic box update checking. If you disable this, then
   # boxes will only be checked for updates when the user runs