Fix handling of scripted commands with redis-cluster hash strategy.

A missing "use" directive was preventing the hash strategy to properly
use the specific methods of Predis\Command\ScriptedCommand, falling back
to analyzing the raw arguments array of the command.

tests/Predis/Cluster/RedisClusterHashStrategyTest.php

@@ -186,7 +186,7 @@ class RedisClusterHashStrategyTest extends StandardTestCase
         $command->expects($this->once())
                 ->method('getScript')
                 ->will($this->returnValue('return true'));
-        $command->expects($this->exactly(1))
+        $command->expects($this->exactly(2))
                 ->method('getKeysCount')
                 ->will($this->returnValue(1));
         $command->setArguments($arguments);