Since capybara-webkit is broken for JRuby. I installed the poltergeist gem. It uses PhantomJS so I needed to install that too.

$ brew install phantomjs

I modified my features/support/env.rb file by adding the following at the end.

require 'capybara/poltergeist'
Capybara.javascript_driver = :poltergeist

WooHoo! It works. Now I can work on the Tic Tac Toe program again.