merged util.format branch (fixes a lint error and simplifies the code)

lib/layouts.js

@@ -26,40 +26,19 @@ 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 data.shift().toString();
-      case "%d": 
-        return new Number(data.shift());
-      case "%j": 
-        return JSON.stringify(data.shift());
-      default:
-        return match;
-      }
-    });
-  } else {
-    //put it back, it's not a format string
-    data.unshift(format);
-  }
-
-  data.forEach(function (item) {
-    if (output) {
-      output += ' ';
-    }
-    output += util.inspect(item);
-    if (item && item.stack) {
-      output += "\n" + item.stack;
+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 {
+      return item;
     }
   });
+}
 
-  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 = {