A new Chapter 2 for Ruby on Rails Tutorial

Based on reader feedback, I have added a new chapter to Ruby on Rails Tutorial: Chapter 2: A demo app. This new chapter presents a high-level overview of Rails, including a discussion of MVC, REST, and the Rails class hierarchies. As part of this change, I've rewritten parts of Chapter 1, which now creates a "first app" instead of the sample app used in Chapter 3 and beyond. Chapter 2 then creates a second "demo app" for use in the overview. One nice consequence of this is that each of the first three chapters now includes the full arc of application creation (rails command, Git repo initialization, etc.), which should serve to reinforce that important process for new readers.

By the way, the insertion of a new Chapter 2 means that the numbers of all subsequent chapters have increased by one. Luckily, I anticipated this possibility, and my typesetting system uses permalinks almost exclusively, so that (for example) links to what used to be Chapter 7 now automatically link to Chapter 8 instead. (Only links for the occasional sub- or subsubsection will break, and I doubt many people have linked to those.)

In other news, I expect to release a new branch of the tutorial soon, a version designed to use Rails 3 throughout. Initially, it will not be fully compatible with Rails 3, but that's what the Rails 3 Tutorial Brigade is for; I'll be relying on the intrepid Brigade readers to help me ferret out the many changes necessary to make Ruby on Rails Tutorial the most up-to-date introduction to Rails available.