Zhao Lu (aka @zlu) has shared a tutorial he has done using Ruby on Rails and the recently released Tropo Web API. The tutorial shows how to add, or build, the Tropo features to your Rails application in 15 minutes using REST/JSON API. All of this deployed to Heroku for easy application deployment. Then he goes on to show how to use Tunnlr with Rails to punch through firewalls without port forwarding…