organize payment classes
ajust test_payment assets arguments order
Merge pull request #38 from algorich/organize_payment_classes

Organize payment classes
add option to perform a credit card extra validation #39
Merge pull request #40 from algorich/credit_card_extra_validation

Add option to perform a credit card extra validation #39
Fix indentation of code in README
Update CHANGELOG for 0.8.0
Bump version to 0.8.0