#209-payment-notifications

Added: 
mailer
delayed_jobs
the ability to send notification if expiry_date is less than 7 days
code refactoring
tests
![zrzut ekranu z 2014-05-19 17 49 17](https://cloud.githubusercontent.com/assets/6718923/3028220/1e82ff4c-e02a-11e3-83bc-cfe6248dcb13.png)