Automatically clear cache
There are some defaults that ship with D8 in your sites/default configuration files that you can configure during development.

The application portion:

Open development.services.yml in the sites folder 
and add the following block (to disable twig cache)
        parameters:
          twig.config:
            debug : true
            auto_reload: true
            cache: false


There is more information on this Drupal.org node.