Switch to sphinx+rtd for documentation

- mkdocs doesn't support GFMD, so is a different dialect
- recommonmark seems abandoned
- Couldn't get m2r to work

So RST + Sphinx it is!

docs/index.rst

@@ -0,0 +1,27 @@
+The Littlest JupyterHub
+-----------------------
+
+A simple `JupyterHub <https://github.com/jupyterhub/jupyterhub>`_ distribution for
+a small (0-50) number of users on a single server.
+
+Quick Start
+===========
+
+On a fresh Ubuntu 18.04 server, you can install The Littlest JupyterHub with:
+
+.. code-block:: bash
+
+   curl https://raw.githubusercontent.com/yuvipanda/the-littlest-jupyterhub/master/installer/install.bash | sudo bash -
+
+This takes 2-5 minutes to run. When completed, you can access your new JupyterHub
+at the public IP of your server!
+
+If this installation method (``curl <arbitrary-url> | sudo bash -``)
+makes you nervous, check out the :ref:`other installation methods <installation>` we support!
+
+.. toctree::
+   :maxdepth: 1
+
+   requirements
+   install
+   admin