Add backup through dropbox

* Install backup and dropbox gems
* Generate model and other dependant files to /backup
* There may a conflict with schedule.rb as I've modified this file in the delay job branch as well
* Add scheduled backup every 24 hours
* Add BACKUP_README.md which outlines the process I went through to set this up
* The backup gem also offers OpenSSL encryption which is very easy to set up
* Along with encryption, Dropbox offers 2-step verification - I think that this is a very secure option.