Vendor the external cookbooks

Knife-Zero doesn't include Berkshelf support, so vendoring everything in
the repo is convenient again

cookbooks/homebrew/resources/cask.rb

@@ -0,0 +1,14 @@
+actions :cask, :uncask, :install, :uninstall
+default_action :install
+
+attribute :name,
+  name_attribute: true,
+  kind_of: String,
+  regex: /^[\w-]+$/
+
+attribute :options,
+  kind_of: String
+
+def casked?
+  shell_out('/usr/local/bin/brew cask list 2>/dev/null').stdout.split.include?(name)
+end