Freshen up the call4papers app

* Bump Ruby Version to 2.1.5
* Remove debugger (incompatible with Ruby version)
* Add a Codeship banner to README
* Add Shellycloud "Cloudfile" and switch to thin
* Deactivate the Travis Build
* Use "dotenv-deployment" for Shelly Cloud production
* Add Dockerfile + fig.yml for local development /o\
* Drop unused gems: Heroku & NewRelic
* Force SSL in production mode

Combined effort of @bitboxer, @moonglum and @bascht