Issue title: [3.0.0-alpha.0] build-storybook is looking for polyfills.js from @kadira/storybook
 Issue body: ```
Building storybook ...
Failed to build the storybook
Module not found: Error: Cannot resolve 'file' or 'directory' .../node_modules/@kadira/storybook/dist/server/config/polyfills.js in ...
```
 Comments: 
 Comment 0: May be a mistake on my part. Closing for now.
{'source': 'GithubIssues', 'repo_name_with_owner': 'storybooks/storybook', 'issue_id': 229844116, 'repo_stars': 28514.0}