Fix missing use directives.

This miss caused a PHP error when Redis did not return a +QUEUED
reply inside a MULTI / EXEC command.

CHANGELOG.md

@@ -1,3 +1,10 @@
+v0.8.1 (201x-xx-xx)
+
+- __FIX__: a missing use directive in `Predis\Transaction\MultiExecContext`
+  caused PHP errors when Redis did not return `+QUEUED` replies to commands
+  when inside a MULTI / EXEC context.
+
+
 v0.8.0 (2012-10-23)
 ===============================================================================
 

lib/Predis/Transaction/MultiExecContext.php

@@ -17,6 +17,7 @@ use Predis\ClientException;
 use Predis\ClientInterface;
 use Predis\CommunicationException;
 use Predis\ExecutableContextInterface;
+use Predis\Helpers;
 use Predis\NotSupportedException;
 use Predis\ResponseErrorInterface;
 use Predis\ResponseQueued;