#1257807 interface.iDeal: add callbacks to check response data (sha1)
#1257807 add transactionrequest_check
#1257807 add logger.info message
#1257807 delete empty line
#1257807 decode to unicode
#1257807 interface.iDeal: use mixin classes
#1257807 interface: add .lower methods when looking for attributes
#1257807 interface.ideal - instantiate the iDeal interface

Also add a TODO note.
#1257807 add models.iDealTransaction
#1257807 add forms
#1257807 sisow.views.PaymentView

Base PaymentView class to submit payments to iDeal system using
TransactionRequest API endpoint.
#1257807 add signals.transaction_started
#1257807 views: send transaction_started