New Paypal button
New payment method buttons
Merge pull request #749 from sharetribe/new-buttons

New buttons
Fix bug if error response does not have data
Fix: payment_sum should be payment_total
Merge pull request #751 from sharetribe/minor-paypal-fixes

Minor paypal fixes
Add transaction transitions from paypal events

* preauthorized to paid
* preauthorized to pending_ext
* pending_ext to paid