stop mutating the arguments when calling multi

This copies the arguments for a multi command instead of mutating the passed in arrays. This allows users to log the commands that gave an error if the multi command errors.

lib/pipeline.js

@@ -182,8 +182,9 @@ Pipeline.prototype.sendCommand = function (command) {
 Pipeline.prototype.addBatch = function (commands) {
   for (var i = 0; i < commands.length; ++i) {
     var command = commands[i];
-    var commandName = command.shift();
-    this[commandName].apply(this, command);
+    var commandName = command[0];
+    var args = command.slice(1)
+    this[commandName].apply(this, args);
   }
 
   return this;