added Jupytext documentation

pages/merlin6/04 jupyterhub/jupytext.md

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+---
+title: Jupytext - efficient editing
+#tags:
+#keywords:
+last_updated: 30 September 2019
+#summary: ""
+sidebar: merlin6_sidebar
+permalink: /merlin6/jupytext.html
+---
+
+[Jupytext](https://github.com/mwouts/jupytext) is a Jupyter serverextension that allows creating a text file from a notebook that can be kept in sync with it. The file can be created in a number of formats, e.g. *markdown, *.py (light Script)*, and others. You can then efficiently work on that file using an IDE or text editor. `Jupytext` will keep the both the notebook and this **paired** file in sync.
+
+## Creating a paired file in python format for efficient refactoring
+
+From your notebook, go to the `file` menu and navigate to the `jupytext` submenu. Select the **light script** pairing option. This will create a `*.py` file version with the same basename as your notebook file.
+
+{% include image.html file="jupytext_menu.png" caption="Jupytext menu" max-width=501 %}
+
+You can edit that file separately in your favourite python editor. The markdown text parts will be conserved in the file in the form of python comments.
+
+When you save the file and do a browser page reload of your jupyter notebook, you will see all the changes caried over into your jupyter notebook.
+
+## Further information
+
+Please refer to
+  * [the Jupytext FAQ](https://jupytext.readthedocs.io/en/latest/faq.html)
+  * [the Jupytext documentation](https://jupytext.readthedocs.io/en/latest/index.html)