This repo is a bit outdated. See the code examples in our Configuration Entities tutorials for up-to-date code. https://drupalize.me/series/configuration-entities
The master branch should be a starting point with the latest version of Drupal plus Drupal Console. The config/sync directory should be removed and added to a separate branch for the Configuration Sync Directory Setup tutorial, since that is where we walk through how to add and set up config/sync.