Add a new documentation tool: MkDocs

MkDocs is a new and popular documentation tool written in Python. It's supported by ReadTheDoc.org.

docs/writing/documentation.rst

@@ -162,3 +162,8 @@ Epydoc_
     Epydoc is discontinued. Use :ref:`sphinx-ref` instead.
 
 .. _Epydoc: http://epydoc.sourceforge.net
+
+MkDocs_
+    MkDocs is a fast, simple and downright gorgeous static site generator that's geared towards building project documentation with Markdown.
+
+.. _MkDocs: http://www.mkdocs.org/