Install tensorflow-addons in tutorials. (#2128)

* nbfmt .

* install addons

* Update README.md

Author: MarkDaoust

docs/README.md

@@ -11,6 +11,15 @@ Any markdown or notebook files in this directory will be published to tensorflow
 `tutorials/_toc.yaml` controls the left-nav on the tutorials tab. Make sure to keep that file up to date.
 Notify the tensorflow/docs team if you need to major changes. 
 
+The preferred formatting for TensorFlow notebooks is to use the [tensorflow/docs](https://github.com/tensorflow/docs) [`nbfmt` tool](https://github.com/tensorflow/docs/tree/master/tools/tensorflow_docs/tools). If modifying a tutorial gives you
+an unreadable diff use the following commands to re-apply the standard formatting:  
+
+```
+pip install git+https://github.com/tensorflow/docs
+python -m tensorflow_docs.tools.nbfmt {path to notebook file or directory}
+```
+
+
 
 ## 2. Generated API docs