A small example of using Bower with Rails 4.
Bower is a generic tool which will resolve dependencies and lock packages down to a version. It runs over Git, and is package-agnostic. A package may contain JavaScript, CSS, images, etc., and doesn't rely on any particular transport (AMD, CommonJS, etc.).
Sprockets recently and silently introduced a basic integration of Bower, a new packet manager by Twitter that ranks among the Top 10 starred projects on GitHub in 2012. This app roughly demonstrates the usage.
I'd be happy if you'd read my blog post for further information.