Do not vendor cookbooks using Berkshelf anymore

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

cookbooks/nginx/attributes/socketproxy.rb

@@ -1,18 +0,0 @@
-#
-# Cookbook:: nginx
-# Attributes:: socketproxy.rb
-#
-
-default['nginx']['socketproxy']['root'] = '/usr/share/nginx/apps'
-default['nginx']['socketproxy']['app_owner'] = 'root'
-default['nginx']['socketproxy']['logname'] = 'socketproxy'
-default['nginx']['socketproxy']['log_level'] = 'error'
-# default['nginx']['socketproxy']['default_app'] = 'default'
-# default['nginx']['socketproxy']['apps'] = {
-#   'default' => {
-#     'prepend_slash' => false,
-#     'context_name' => '',
-#     'subdir' => 'current',
-#     'socket_path' => 'shared/sockets/unicorn.sock'
-#   }
-# }