Added hash accessor methods, which are expected for interoperability with many other frameworks (such as Devise)

Change-Id: Ia5f0293576f4656c09097dc673e5103792784d9f
Reviewed-on: http://review.couchbase.org/33436
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>