Update conf.py

Author: OpenAstroTech

docs/conf.py

@@ -49,4 +49,7 @@
 # Add any paths that contain custom static files (such as style sheets) here,
 # relative to this directory. They are copied after the builtin static files,
 # so a file named "default.css" will overwrite the builtin "default.css".
-html_static_path = ['_static']
+html_static_path = ['_static']
+
+# Needed for RTD build
+master_doc = 'index'