Filter out 0.0.0.0, if ever gotten from Cassandra in split calculation. ...

...Fixes #332.
And I would pull out the code doc to above it, even if you don't want it in docs:

/* An incorrectly configured Cassandra node may send us 0.0.0.0 as the rpc_address.
     If this happens, we replace it with the local address (which must be always != 0.0.0.0) */
def cassandraNode(rpcAddress: InetAddress, localAddress: InetAddress): CassandraNode =