How to create a comment and reply system in Ruby on Rails

This is a tutorial about building a simple comment and reply system with Ruby on Rails. I was looking for a way to build this without a gem. Most tutorials use gems such as closure_tree, or ancestry. This seemed more than what I wanted. I was able to get some guidance from Nick Haskins the author of Playbook Thirty-nine and StackOverflow. You can find the completed project here.