Vendor the external cookbooks

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

cookbooks/composer/recipes/self_update.rb

@@ -0,0 +1,16 @@
+#
+# Cookbook Name:: composer
+# Recipe:: self_update
+#
+# Copyright (c) 2016, David Joos
+#
+
+include_recipe 'composer::install'
+
+execute 'composer-self_update' do
+  cwd node['composer']['install_dir']
+  command 'composer self-update'
+  environment 'COMPOSER_HOME' => Composer.home_dir(node)
+  action :run
+  ignore_failure true
+end