Recommend using bower
The bower package is maintained by the owner of scrollTo. Which means it will be way more up to date and not require a Rails engine.
See the scrollTo README for details on installing with bower.
See the bower-rails README for a guide to getting bower working in your Rails project.
jquery-scrollto-rails
This gem provides the jquery scrollTo project found at http://archive.plugins.jquery.com/project/ScrollTo for the Rails asset pipeline (available since Rails 3.1).
Installation
In your Gemfile, add this line:
gem "jquery-scrollto-rails"
Then, run bundle install.
Add this to 'app/assets/javascripts/application.js':
//= require jquery.scrollTo
That's it!