Add `hd` parameter to GoogleResourceOwner
It allows "locking" to particular domains with user can sign-in
Fix previous merge
Merge pull request #301 from stloyd/feature/google_hd

Add `hd` parameter to GoogleResourceOwner
Add BitBucket resource owner
Merge pull request #300 from stloyd/feature/bitbucket

Add BitBucket resource owner
Prepare code for CSRF protection
Refactor code to use CSRF protection