Ruby-1.9.2 compatible and ready for deploy on Heroku

Made some changes to make your application compatible with ruby-1.9.2 (tested on ruby-1.9.2-p290) and also to make it deployable to Heroku [ http://heroku.com/ ]. The application successfully is running on URL: [ http://hotlinks.herokuapp.com/ ]

 * For ruby-1.9.2 only the way the local files are required is changed
 * For Heroku, added some system files (config.ru, Procfile etc.) and made it possible to use RedisToGo Heroku addon (free Redis) - [ http://devcenter.heroku.com/articles/redistogo ], which is configured with the ENV["REDISTOGO_URL"] environment variable.