Support for Redis 5.0 streams (XADD/XREAD/XRANGE) in RedisIO

Redis 5.0 and later support an append-only log data structure called a "stream" – each element has a unique incrementing ID and contains one or more string:string key-value pairs.

This seems like a gimme for a stream processing platform to support, and in fact Jedis already has support for XADD/XREAD/XRANGE in it, but the current redisIO Read and Write classes only support pcollections of single KVs and thus will need some additional work to support streams.