*   The signature of the `tf.contrib.data.rejection_resample()` function has
    been changed. It now returns a function that can be used as an argument to
    `Dataset.apply()`.
*   Remove `tf.contrib.data.Iterator.from_dataset()` method. Use
    `Dataset.make_initializable_iterator()` instead.
*   Remove seldom used and unnecessary `tf.contrib.data.Iterator.dispose_op()`.
*   Reorder some TF-GAN loss functions in a non-backwards compatible way.