Update the README

Since we are using rst now, let's convert the README to rst as well. I
also removed some obsolete Jekyll instructions and replaced them with
the proper Sphinx ones.

README.rst

@@ -0,0 +1,35 @@
+Syncthing Docs
+==============
+
+This repo is the source behind http://docs.syncthing.net/.
+
+Editing
+-------
+
+To edit the documentation you need a GitHub account. Once you have created one
+and logged in, you can edit any page by navigating to the corresponding file and
+clicking the edit (pen) icon. This will create a so called "fork" and a "pull
+request", which will be approved by one of the existing documentation team
+members. Once you haveve made a contribution or two, you can be added to the
+documentation team and perform edits without requiring approval.
+
+In the long run, learning to use Git_ and running Sphinx_ on your computer is
+beneficial.
+
+Structure
+---------
+
+The documentation is divided into an index page (``index.rst``) and various
+subsections. The sections are:
+
+- Introductory information in ``intro``.
+- Information for users in ``users``.
+- Information for developers in ``dev``.
+
+The documentation uses the `rst format`_. For a starting point check out the
+`reStructuredText Primer`_
+
+.. _Git: http://www.git-scm.com/
+.. _Sphinx: http://sphinx-doc.org/
+.. _`rst format`: http://docutils.sourceforge.net/docs/ref/rst/restructuredtext.html
+.. _`reStructuredText Primer`: http://sphinx-doc.org/rest.html