How to upgrade your application to Rails 4
I'm writing a leanpub book on how to upgrade your Rails 3 application to Rails 4. It covers all new features introduced in Rails 4 and contains the deprecated features as well. You can follow along with the included upgrade checklist to upgrade all breaking changes. Here is the link: https://www.leanpub.com/upgradetorails4. Feedback and suggestions are very welcome.