Add notice in the example of servers-side scripting with Lua.

examples/ServerSideScripting.php

@@ -11,6 +11,8 @@
 
 require 'SharedConfigurations.php';
 
+// This example will not work with versions of Redis < 2.6.
+//
 // Additionally to the EVAL command defined in the current development profile, the new
 // Predis\Commands\ScriptedCommand base class can be used to build an higher abstraction
 // for our "scripted" commands so that they will appear just like any other command on