Change Cascading Tap SinkMode to UPDATE

Change Tap and Sink mode to UPDATE since it seems that
CascadingConnector will try to delete them otherwise resulting in
exceptions

Fix #260

(cherry picked from commit 78508ec2442e01a9c109f2c82d0d08d36d92ca25)
Update to Cascading 2.5.6

(cherry picked from commit 6402d788e9643360cc6fc0c09c19df86fa3da037)