[SPARK-1981] Add AWS Kinesis streaming support

ok, i've moved this method to a private helper class.  it's a static method, so from a testability standpoint, it's awkward to have this part of a non-static class such as KinesisReceiver.  

otherwise, i would need to instantiate a KinesisReceiver with a bunch of mocks just to test this method.

this seems like a good compromise, but let me know if you feel otherwise.