Upgrade Cassandra driver to version 2.1.9
Upgrade Cassandra driver to version 2.1.9

- closes #237

ianclegg/eventuate,RBMHTechnology/eventuate,RBMHTechnology/eventuate,RBMHTechnology/eventuate,RBMHTechnology/eventuate,ianclegg/eventuate,RBMHTechnology/eventuate,ianclegg/eventuate,ianclegg/eventuate,ianclegg/eventuate