Merge pull request #199 from lulurun/fix_file_appender

fix shutdown method: make sure to callback when write completed immediat...

lib/appenders/file.js

@@ -85,6 +85,8 @@ function shutdown(cb) {
       file.once('drain', function() {
         file.end(done);
       });
+    } else {
+      file.end(done);
     }
   }, cb);
 }