Display Heroku app release name in the app's footer.
See: http://stackoverflow.com/questions/8792716/reflecting-heroku-push-version-within-the-app
Requires the following:
% heroku config:add HEROKU_API_KEY=<your-API-key-here>
% heroku config:add HEROKU_FC_APP_NAME=<your-Heroku-app-name-here>