*   `tf.losses.*` do not add to the global collection when executing eagerly (to
    avoid leaking memory).
*   Support different summary and checkpoint directories in
    `tf.train.MonitoredTrainingSession()`.
*   Added IndRNN, IndyGRU, and IndyLSTM cells to `tf.contrib.rnn`.
*   Add safe static factory functions for SparseTensor and convert all CHECKs to
    DCHECKs. Using the constructor directly is unsafe and deprecated.