Update README.rst

Fix formatting errors.

{{cookiecutter.app_name}}/README.rst

@@ -26,8 +26,11 @@ Then run the following commands to bootstrap your environment.
     python manage.py server
     
 You will see a pretty Welcome screen.
+
 If you have already installed your database.
 
+::
+
     python manage.py db init
     python manage.py db migrate
     python manage.py db upgrade