bugfix in docs

docs/conf.py

@@ -41,6 +41,7 @@
 # This pattern also affects html_static_path and html_extra_path.
 exclude_patterns = ['_build', 'Thumbs.db', '.DS_Store']
 
+master_doc = 'index'
 
 # -- Options for HTML output -------------------------------------------------
 
@@ -52,4 +53,4 @@
 # 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']