message: tfdbg: Add link to TensorBoard Debugger Plugin
  from the CLI documentation
  RELNOTES: tfdbg: TensorFlow Debugger's graphical user interface (GUI),
  the [TensorBoard Debugger Plugin](https://github.com/tensorflow/tensorboard/blob/master/tensorboard/plugins/debugger/README.md), is now in alpha.
diff: @@ -23,8 +23,13 @@ debuggers such as Python's `pdb` due to TensorFlow's computation-graph paradigm.
  > installed using `pip install <your_version>.whl`, however curses on Windows
  > may not work as reliably as curses on Linux or Mac.
  -This tutorial demonstrates how to use the **tfdbg** command-line interface
  -(CLI) to debug the appearance of [`nan`s](https://en.wikipedia.org/wiki/NaN)
  +> NOTE: This guide focuses on the command-line interface (CLI) of tfdbg. For
  +> guide on how to use the graphical user interface (GUI) of tfdbg, i.e., the
  +> **TensorBoard Debugger Plugin**, please visit
  +> [its README](https://github.com/tensorflow/tensorboard/blob/master/tensorboard/plugins/debugger/README.md).
  +
  +This tutorial demonstrates how to use the **tfdbg** CLI to debug the appearance
  +of [`nan`s](https://en.wikipedia.org/wiki/NaN)
  and [`inf`s](https://en.wikipedia.org/wiki/Infinity), a frequently-encountered
  type of bug in TensorFlow model development.
  The following example is for users who use the low-level
  @@ -806,3 +811,13 @@ sess.run(b)
  the constant-folding would not occur and `tfdbg` should show the intermediate
  tensor dumps.
  +
  +**Q**: Is there a GUI for tfdbg?
  +
  +**A**: Yes, the **TensorBoard Debugger Plugin** is the GUI of tfdbg.
  + It offers features such as inspection of the computation graph,
  + real-time visualization of tensor values, continuation to tensor
  + and conditional breakpoints, and tying tensors to their
  + graph-construction source code, all in the browser environment.
  + To get started, please visit
  + [its README](https://github.com/tensorflow/tensorboard/blob/master/tensorboard/plugins/debugger/README.md).
  