1. Update dependencies
- Add font-awesome as dependency
- Switch to Bootstrap 4 dev branch
- Remove eslint airbnb style (we're not using it)
2. Imported images and fonts should go into dist/images
and dist/fonts, respectively
3. Only lint our own code, not external code (fixes#1633)
Remove path.extname() check to fix build:production task.
Currently path.extname() is being supplied an object when it expects a string, resulting in a fatal error during production builds.
Removal is the cleanest solution as it's an unnecessary check, assets[name] will always be an object.
