Adds comments to methods and classes and refactors Authorization class name to PaymentAuthorization
Updates README
Updates README
Refactoring for using just one transaction at a time
Updates README
Adds tests for paypal authorization, execution and capture of payment
WIP Refactoring Payment and Payment Authorization builders
Refactorign for Payment and PaymentAuthorization builders
Removes useless "use" statement
Refactoring of authorization interface
Refactoring of model builders. Adds documentation and examples.
Updates README
Updates README