Merge pull request #3 from sharik709/recurring-payments

added recurring or subscription payment functionalities

payment profile typo fixed.

added support for php7.4

updated readme.md

- Fixed namespace issue with tests

- Added ability to check if credentials are provided and then throw
exception if not.
- Added new columns for migration to take brand, type and last 4
- Added ability to store source data ( brand, type and last 4)

added more details on readme page. Which informs user on what is impo…

…rtant in order to process a charge

added charging functionality to charge a customer's payment profile