pass loggly http client errors to winston continuation

lib/winston-loggly.js

@@ -108,9 +108,9 @@ Loggly.prototype.log = function (level, msg, meta, callback) {
   //
   // Helper function for responded to logging.
   //
-  function logged() {
+  function logged(err) {
     self.emit('logged');
-    callback(null, true);
+    callback(err, true);
   }
 
   return meta.tags