message: Fix issues in doc `tf.Placeholder` should be `tf.placeholder`
  This fix fixes issues in the doc (data_feeder.py) where
  `tf.Placeholder` should be `tf.placeholder`
diff: @@ -857,8 +857,8 @@ class DaskDataFeeder(object):
  """Returns a function, that will sample data and provide it to placeholders.
  Args:
  - input_placeholder: tf.Placeholder for input features mini batch.
  - output_placeholder: tf.Placeholder for output labels.
  + input_placeholder: tf.placeholder for input features mini batch.
  + output_placeholder: tf.placeholder for output labels.
  Returns:
  A function that when called samples a random subset of batch size
  