Update conf.py

source/conf.py

@@ -29,7 +29,7 @@ import os
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
 # ones.
 extensions = [
-    'sphinx.ext.autodoc', 'sphinx.ext.mathjax', 'sphinx.ext.todo',
+    'sphinx.ext.autodoc', 'sphinx.ext.mathjax', 'sphinx.ext.todo', 'sphinx_rtd_theme', 
 ]
 
 [extensions]