fix license year, output dir

examples/handwritten_number_recognition/mnist.py

-# Copyright (c) 2019 PaddlePaddle Authors. All Rights Reserved.
+# Copyright (c) 2020 PaddlePaddle Authors. All Rights Reserved.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -60,7 +60,7 @@ def main():
               val_dataset,
               epochs=FLAGS.epoch,
               batch_size=FLAGS.batch_size,
-              save_dir='mnist_checkpoint')
+              save_dir=FLAGS.output_dir)
 
 
 if __name__ == '__main__':
@@ -81,7 +81,10 @@ if __name__ == '__main__':
     parser.add_argument(
         "-b", "--batch_size", default=128, type=int, help="batch size")
     parser.add_argument(
-        "--output-dir", type=str, default='output', help="checkpoint save dir")
+        "--output-dir",
+        type=str,
+        default='mnist_checkpoint',
+        help="checkpoint save dir")
     parser.add_argument(
         "-r",
         "--resume",