Do not vendor cookbooks using Berkshelf anymore

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

cookbooks/composer/libraries/composer.rb

@@ -1,10 +0,0 @@
-# Composer module
-module Composer
-  def self.install_dir(node)
-    node['composer']['install_dir']
-  end
-
-  def self.home_dir(node)
-    node['composer']['home_dir'] || install_dir(node)
-  end
-end