2 0 stable

Hi again, 

I fixed some more problems with the skrill module and now it is fully function 
with IPN status updates and returning properly back to the shop from within the iframe 

The issues were related mainly to accessing attributes (A StateMachine::InvalidTransition occurred in checkout) and are similar to the issues described here https://github.com/spree/spree_paypal_express/issues/68

I have tested everything and it works as expected (order is marked properly as paid and ready for shipping)

Please let me know if you have any comments or critic 

Best Regards,
Alex