When DataHandler.findUser() returns None, (incorrect user/password), Returns InvalidGrant with a more decriptive error message
Merge pull request #22 from gertjana/0.8.0_issue_20

When username/password is incorrect gives a more decriptive error message
update a version for Playframework 2.2
First pass on moving the library to support a non-blocking data-handler trait.

Additional Comments:
All tests passing, but probably needs a closer inspection particularly on some of the grants that throw exceptions as I don't believe those are currently being tested for each exception type.
update README for how to create your trait