Do not vendor cookbooks using Berkshelf anymore

Instead, use the Berkshelf support in knife-solo and the
vagrant-berkshelf plugin on Vagrant

cookbooks/homebrew/resources/cask.rb

@@ -1,14 +0,0 @@
-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