*   `uniform_unit_scaling_initializer()` no longer takes a `full_shape` arg,
    instead relying on the partition info passed to the initializer function
    when it's called.
*   The NodeDef protocol message is now defined in its own file `node_def.proto`
    `instead of graph.proto`.
*   `ops.NoGradient` was renamed `ops.NotDifferentiable`. `ops.NoGradient` will
    be removed soon.