Added support for sharded pub/sub consumer (#1303)

* Added support for sharded pub/sub consumer

* Removed query parameter

* Fix typo

* Codestyle fixes

* Added support for sharded pub/sub against DispatcherLoop

* Updated sharded consumer example to subscribe on differend shard channels

* Added test coverage

* Removed cluster condition for pub/sub

* Codestyle fixes

* Changed socket read interface, added parameters as dependency to cluster connection

* Added for interface consistency

* Updated method description

* Updated method description

* Removed redundant exception

* Codestyle fix

* Updated README

* Mark tests as relay-incompatible

* Mark tests as relay-incompatible

* Mark tests as relay-incompatible

* Moved sharded pub/sub functionality to new consumer

* Codestyle fixes

* Resolve context depends on connection type

* Codestyle fixes

src/ClientContextInterface.php

@@ -330,6 +330,9 @@ use Predis\Command\Redis\Container\Search\FTCURSOR;
  * @method $this save()
  * @method $this slaveof($host, $port)
  * @method $this slowlog($subcommand, $argument = null)
+ * @method $this spublish(string $shardChannel, string $message)
+ * @method $this ssubscribe(string ...$shardChannels)
+ * @method $this sunsubscribe(string ...$shardChannels)
  * @method $this time()
  * @method $this command()
  * @method $this geoadd($key, $longitude, $latitude, $member)