Do not vendor cookbooks using Berkshelf anymore

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

cookbooks/apt/templates/01proxy.erb

@@ -1,11 +0,0 @@
-Acquire::http::Proxy "http://<%= @server['host'] %>:<%= @server['port'] %>";
-<% if @server['proxy_ssl'] %>
-Acquire::https::Proxy "http://<%= @server['host'] %>:<%= @server['port'] %>";
-<% else %>
-Acquire::https::Proxy "DIRECT";
-<% end %>
-<% unless @server['cache_bypass'].nil? %>
-<% @server['cache_bypass'].each do |bypass, type| %>
-Acquire::<%= type %>::Proxy::<%= bypass %> "DIRECT";
-<% end %>
-<% end %>