message: Change link to README.md in module comments.
diff: This module provides a subset of numpy APIs, built on top of TensorFlow
  operations. Please see documentation here:
  -https://github.com/tensorflow/tensorflow/tree/master/tensorflow/python/ops/numpy_ops.
  +https://github.com/tensorflow/tensorflow/tree/master/tensorflow/python/ops/numpy_ops/README.md
  """
  # TODO(wangpeng): Append `np_export`ed symbols to the comments above.
  