Updated CHANGELOG.

CHANGELOG

@@ -64,6 +64,24 @@ v0.6.0
   * CommandPipeline and MultiExecBlock return their instances when invoking 
     commands, thus allowing method chaining in pipelines and multi-exec blocks.
 
+  * Introduced the Predis\Pipeline\IExecutor interface. Classes implementing 
+    this interface are now used internally by the Predis\CommandPipeline class 
+    to change the behaviour of the pipeline when writing/reading commands from 
+    one or multiple servers. Here is the list of the default executors:
+      - Predis\Pipeline\StandardExecutor
+        Exceptions generated by server errors might be thrown depending on the 
+        options passed to the client (see "throw_on_error"). Instead, protocol 
+        or network errors always throw exceptions. This is the default executor 
+        for single and clustered connections and shares the same behaviour of 
+        Predis 0.5.x.
+      - Predis\Pipeline\SafeExecutor
+        Exceptions generated by server, protocol or network errors are not 
+        thrown, instead they are returned in the response array as instances of 
+        ResponseError or CommunicationException.
+      - Predis\Pipeline\SafeClusterExecutor
+        This executor shares the same behaviour of Predis\Pipeline\SafeExecutor 
+        but it is geared towards clustered connections.
+
   * MultiExecBlock instances can handle the new DISCARD command.
 
   * The GET parameter for the SORT command now accepts also multiple key