remove vagrant-cachier configuration in favor of enabling it globally via `~/.vagrant.d/Vagrantfile`
back to Ubuntu 12.04 LTS; correct URL of sample-toplevel-cookbook
use 10.x.x.x network (33.x.x.x is not a private one)
remove plugins.json because fgrehm/bindler is not supported anymore with Vagrant 1.6 :-(
adapt README
fix configuration for vagrant-toplevel-cookbooks