*   Added `tf.contrib.framework.filter_variables` as a convenience function to
    filter lists of variables based on regular expressions.
*   `make_template()` takes an optional `custom_getter_ param`.
*   Added comment about how existing directories are handled by
    `recursive_create_dir`.
*   Added an op for QR factorizations.
*   Divides and mods in Python API now use flooring (Python) semantics.

      absl::Span<const int64_t> input_tensor_id,
      absl::Span<const tensorflow::DataType> input_dtypes,
      const std::function<BackwardFunction*()>& backward_function_getter,
      const std::function<void(BackwardFunction*)>& backward_function_deleter);

  void DeleteTrace(int64_t tensor_id);

  // Consumes the internal state of the tape (so cannot be called more than