Add a para about sphinx <-> epydoc.

doc/intro.rst

@@ -5,6 +5,11 @@ This is the documentation for the Sphinx documentation builder.  Sphinx is a
 tool that translates a set of reStructuredText_ source files into various output
 formats, automatically producing cross-references, indices etc.
 
+The focus is on hand-written documentation, rather than auto-generated API docs.
+Though there is limited support for that kind of docs as well (which is intended
+to be freely mixed with hand-written content), if you need pure API docs have a
+look at `Epydoc <http://epydoc.sf.net/>`, which also understands reST.
+
 .. XXX web app
 
 Prerequisites