v0.4.3

• It's now possible to set up a keepalive interval for a session, which is useful for rarely used sessions (e.g. ones querying once an hour for statistical purposes)
• use_keyspace request now has a timeout, equal to the specified connect_timeout, with a default value of 5 seconds
• UDT fields from CqlValue can now be borrowed
• SerializedValuesIterator implementation got substantially simplified