note about default welcome page not showing when deploying to Heroku and using Rails 4

Some students using Rails 4 were confused at the last Railsbridge event when they hit the end of this step:
http://installfest.railsbridge.org/installfest/create_and_deploy_a_rails_app

Rails 4 doesn't show the Welcome Aboard default page on Heroku. It only shows it on localhost.

Please note that I only added line 259. Not sure why the commit says I edited line 183. I couldn't figure out how to make the commit without showing that line as edited.