Babel not auto-configured when used in an addon

I just tried to use `ember-decorators` in an addon and was happy to see that https://github.com/rwjblue/ember-decorators/commit/93289926e8bfbe2b0f4aa4d4ccbc55b9cd80662e removed the setup section from the README, including the setup for usage in addons.

However, I still had to include the `init` patch in my addon's `index.js`. Was that piece of the README removed by accident or should this work without manually adding the plugins in `index.js`?

Start with the README change in commit 93289926e8bfbe2b0f4aa4d4ccbc55b9cd80662e and inspect the addon's index.js init patch described in the report. Determine whether addon use should configure Babel automatically; done means the expected behavior is documented and the manual plugin setup is either unnecessary or clearly required.

Written by the indexing model from the issue text.