message: Fix deprecated div
  While running test I noticed the following warning:
  ```
  WARNING:tensorflow:From /usr/local/lib/python2.7/dist-packages/tensorflow/python/ops/nn_ops.py:2744: div (from tensorflow.python.ops.math_ops) is deprecated and will be removed in a future version.
  Instructions for updating:
  Deprecated in favor of operator or tf.math.divide.
  ```
  This fix fixes the deprecated warning.
diff: @@ -2741,7 +2741,7 @@ def dropout(x, keep_prob, noise_shape=None, seed=None, name=None): # pylint: di
  noise_shape, seed=seed, dtype=x.dtype)
  # 0. if [keep_prob, 1.0) and 1. if [1.0, 1.0 + keep_prob)
  binary_tensor = math_ops.floor(random_tensor)
  - ret = math_ops.div(x, keep_prob) * binary_tensor
  + ret = math_ops.divide(x, keep_prob) * binary_tensor
  if not context.executing_eagerly():
  ret.set_shape(x.get_shape())
  return ret
  