Update gitignore file

Signed-off-by: Tim Smith <tsmith@chef.io>

.gitignore

@@ -34,17 +34,18 @@ _yardoc
 doc/
 .idea
 
-#chef stuff
+# chef stuff
 Berksfile.lock
 .kitchen
 .kitchen.local.yml
 vendor/
 .coverage/
 .zero-knife.rb
+Policyfile.lock.json
 Cheffile.lock
 .librarian/
 
-#vagrant stuff
+# vagrant stuff
 .vagrant/
 .vagrant.d/
 .kitchen/