Handle creditcard payments

[stefantalen]

In the current version only iDeal is support as a payment method

[pedzed]

@stefantalen Could you add descriptions to your issues? Perhaps others can help in fixing the issues. If the issues are fixed, please close them to prevent confusion.

[stefantalen]

Updated the description(s), I've only implemented iDeal payments because the project this library is being used in had only need of that. All other payment methods aren't supported.

Feel free to add them or if you're looking for a more robust library you should check out OmniPay, which has more gateways supported other than Rabobank OmniKassa