fix ember-cli-addon

- [ ] get @rwjblue to review
- [ ] ensure needed files are published
@rwjblue and I were talking about allowing add-ons to call `addBowerPackageToProject` within the ember-addon-main (without the need for a blueprint) yesterday, but [AKAIK that ability hasn't landed](https://github.com/stefanpenner/ember-cli/commits/master)