Add sphinx_rtd_theme to import and extensions

docs/conf.py

@@ -14,6 +14,7 @@
 
 import sys
 import os
+import sphinx_rtd_theme
 
 # If extensions (or modules to document with autodoc) are in another directory,
 # add these directories to sys.path here. If the directory is relative to the
@@ -28,7 +29,7 @@ import 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.todo']
+extensions = ['sphinx.ext.todo', 'sphinx_rtd_theme']
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']