fix(google): move $deferred inside of the GoogleTokenVerifier injector

- Move the $deferred object to GoogleTokenVerifier and inside $injector.invoke and return directly $deferred.promise
- Update the demo to call $rootScope.$apply inside the verifyAsync then()

Closes #1, #8
Merge pull request #9 from colin-bellino/fix-deferred

Fix the promise of the GoogleTokenVerifier