Switch to `node-cassandra-cql`.

Remove pre-attached `"error"` listener. Use quorum consistency by
default for all reads and writes. `CassandraAdapter#createKeyspace()`
should use a replication factor of 1 when provisioning a keyspace,
as it will be impossible to reach quorum with a factor of 3 when
running locally.

Lock down dependency version. Use my fork of `node-cassandra-cql` until
jorgebray/node-cassandra-cql#83 is merged.
Update unit tests.
Rename to `polyclay-cassandra-cql`.