add autodoc, numpydoc and doctest to sphinx to generate API doc

doc/conf.py

@@ -25,7 +25,13 @@ import sys, os
 
 # Add any Sphinx extension module names here, as strings. They can be extensions
 # coming with Sphinx (named 'sphinx.ext.*') or your custom ones.
-extensions = ['sphinx.ext.pngmath']
+extensions = [
+	'sphinx.ext.pngmath',
+	'sphinx.ext.autodoc',
+	'sphinx.ext.doctest',
+	'sphinx.ext.autosummary',
+	'numpydoc',  # to preprocess docstrings
+	]
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']