stack traces when util.log's an error

lib/util.js

@@ -30,12 +30,16 @@ var util = {
   
   log: function () {
     if (util.debug) {
-      var copy = [];
-      for (var i = 0; i < arguments.length; i++) {
-        copy[i] = arguments[i];
-      }
+      var err = false;
+      var copy = Array.prototype.slice.call(arguments);
       copy.unshift('PeerJS: ');
-      console.log.apply(console, copy);
+      for (var i = 0, l = copy.length; i < l; i++){
+        if (copy[i] instanceof Error) {
+          copy[i] = '(' + copy[i].name + ') ' + copy[i].message;
+          err = true;
+        }
+      }
+      err ? console.error.apply(console, copy) : console.log.apply(console, copy);
     }
   },