working zippy in-app payments (bug 1040949)
Create Buyer at Persona login (bug #1040925)

- Check and create buyer when Persona login takes place
- Remove create buyer from PIN creation time in API/Views
- Update tests
Merge pull request #530 from JaredKerim-Mozilla/1040132

    Create Buyer at Persona login (bug #1040925)
Merge pull request #529 from kumar303/zippy-inapp

working zippy in-app payments (bug 1040949)