Changed layouts to use util.format instead of my own implementation

lib/layouts.js

@@ -24,37 +24,19 @@ var dateFormat = require('./date_format')
     , OFF: "grey"
   };
 
-function formatLogData(logData) {
-    var output = ""
-      , data = Array.isArray(logData) ? logData.slice() : Array.prototype.slice.call(arguments)
-      , format = data.shift();
-
-    if (typeof format  === "string") {
-        output = format.replace(replacementRegExp, function(match) {
-            switch (match) {
-            case "%s": return new String(data.shift());
-            case "%d": return new Number(data.shift());
-            case "%j": return JSON.stringify(data.shift());
-            default:
-                return match;
-            };
-        });
+function wrapErrorsWithInspect(items) {
+  return items.map(function(item) {
+    if ((item instanceof Error) && item.stack) {
+      return { inspect: function() { return util.format(item) + '\n' + item.stack; } };
     } else {
-        //put it back, it's not a format string
-        data.unshift(format);
+      return item;
     }
+  });
+}
 
-    data.forEach(function (item) {
-        if (output) {
-            output += ' ';
-        }
-        output += util.inspect(item);
-        if (item && item.stack) {
-            output += "\n" + item.stack;
-        }
-    });
-
-    return output;
+function formatLogData(logData) {
+  var data = Array.isArray(logData) ? logData : Array.prototype.slice.call(arguments);
+  return util.format.apply(util, wrapErrorsWithInspect(data));
 }
 
 var styles = {