message: Add link to WORKSPACE, which sets the TF version
diff: @@ -23,6 +23,9 @@ sudo ldconfig
  Now, you're ready to compile TensorFlow from source:
  +Currently this builds Tensorflow version **1.13.1** (see
  +[WORKSPACE](../WORKSPACE) for details)
  +
  ```shell
  sudo apt-get install zip
  ./cc/configure_tensorflow.sh
  