Vendor the external cookbooks

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

cookbooks/composer/libraries/composer.rb

@@ -0,0 +1,10 @@
+# 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