I am the author - this is a detailed analysis of the gems used in the 2013 Rails Rumble. It ends up being a snapshot of gem popularity and trends. A lot of surprises in here, at least for me.
Interesting to see the turbolinks. I have yet to use them, currently migrating a mid-size app to 4 and will try them out. But, that was my experience with jQuery mobile's similar ajax link by default strategy. Their great, until you have any kind of form and then you're soon disabling the ajax part and appreciating a fresh, clean dom being loaded.
Did you just look at the Gemfiles?<p>Especially things like CoffeeScript get put in the Gemfile by the default generator and there's still a big chance, that no line of CoffeeScript is in the project after all ...