vagrant: switch to 'official' debian/wheezy64

vagrant/Vagrantfile

 API_VERSION = "2"
 
 Vagrant.configure(API_VERSION) do |config|
-  config.vm.box = "debian-wheezy-64"
-  config.vm.box_url = "http://basebox.libera.cc/debian-wheezy-64.box"
+  config.vm.box = "debian/wheezy64"
+  config.vm.box_url = "debian/wheezy64"
 
   config.vm.provision "shell" do |s|
     s.path = "setup.sh"