Add an internals doc to the documentation

Sometimes having narrative text describing how objects hang together it
handy for knowing what to do.

Change-Id: Ib12af2d993740d82b4f43de74b11ecefd1cd363a
diff --git a/doc/source/conf.py b/doc/source/conf.py
index 9e0d2c7..f8ae368 100644
--- a/doc/source/conf.py
+++ b/doc/source/conf.py
@@ -25,7 +25,11 @@
 
 # Add any Sphinx extension module names here, as strings. They can be extensions
 # coming with Sphinx (named 'sphinx.ext.*') or your custom ones.
-extensions = [ 'sphinxcontrib.blockdiag', 'sphinxcontrib.programoutput' ]
+extensions = [
+    'sphinx.ext.autodoc',
+    'sphinxcontrib.blockdiag',
+    'sphinxcontrib.programoutput'
+]
 #extensions = ['sphinx.ext.intersphinx']
 #intersphinx_mapping = {'python': ('http://docs.python.org/2.7', None)}