Builder#use returns self, for chaining

lib/vagrant/action/builder.rb

@@ -52,6 +52,8 @@ module Vagrant
         else
           self.stack << [middleware, args, block]
         end
+
+        self
       end
 
       # Inserts a middleware at the given index or directly before the

test/vagrant/action/builder_test.rb

@@ -28,6 +28,10 @@ class ActionBuilderTest < Test::Unit::TestCase
     end
 
     context "adding to the stack" do
+      should "return self" do
+        assert @instance.equal?(@instance.use(1))
+      end
+
       should "add to the end" do
         @instance.use 1
         @instance.use 2