fix order for GET requests, it is not OrderBy but simply order
add UpdatedDateUTC to Payments, retrieve as updated_at on the object
Merge branch 'add_updated_at_to_payments' into develop
Added functionality for get_payments
Removed unused invalid payment id constant
Removed pry from test and gateway param from payment from_xml
Merge pull request #59 from felixibel/add_get_payments

Add get payments