Markdown version of Cytoscape manual

Kozo's instructions:

1. I exported http:https://wiki.cytoscape.org/Cytoscape_3/UserManual to a docbook xml. (https://github.com/kozo2/cytoscape3-usermanual/blob/master/UserManual.xml)

2. I converted UserManual.xml to UserManual.md (https://github.com/kozo2/cytoscape3-usermanual/blob/master/UserManual.md) with pandoc -f docbook -t markdown -s UserManual.xml -o UserManual.md

3. I separated UserManual.md per chapter manually. (https://github.com/kozo2/cytoscape3-usermanual/tree/master/docs)

4. I built and deployed 3. with mkdocs and readthedocs.

Additionally:

1. Create a new project in ReadTheManual, and create a WebHook from GitHub to ReadTheDocs via http:https://docs.readthedocs.org/en/latest/webhooks.html

2. Text is processed by Sphinx, which is documented here: http:https://www.sphinx-doc.org/en/stable/contents.html