Fix a couple of namespacing issues with client exceptions in connection classes (ISSUE #24).

lib/Predis/Network/ConnectionBase.php

@@ -5,6 +5,7 @@ namespace Predis\Network;
 use Predis\Utils;
 use Predis\ICommand;
 use Predis\ConnectionParameters;
+use Predis\ClientException;
 use Predis\CommunicationException;
 use Predis\Protocols\IRedisProtocol;
 

lib/Predis/Network/ConnectionCluster.php

@@ -3,6 +3,7 @@
 namespace Predis\Network;
 
 use Predis\ICommand;
+use Predis\ClientException;
 use Predis\Distribution\IDistributionStrategy;
 
 class ConnectionCluster implements IConnectionCluster, \IteratorAggregate {