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
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
Refactoring and add test case #18
Merge branch 'master' into lifeway-master

Conflicts:
	scala-oauth2-core/src/main/scala/scalaoauth2/provider/GrantHandler.scala
Merge branch 'lifeway-master'
fix description
add OAuth2Provider customize supporting grant types
improve error messages
add description for DataHandler with Future
enhance validating to parse Authentication header
testing for scala 2.10.x and 2.11.x on travis