Depend on the latest core-io SNAPSHOT

Change-Id: Icf29de8990c0a347e04638e45f2b106ca15d6dad
Reviewed-on: http://review.couchbase.org/43405
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>
Reviewed-by: Simon Baslé <simon@couchbase.com>