NPM install warning for AirBnB eslint profile

This currently doesn't prevent eslint from functioning correctly, but it raises an annoying warning message on every run of npm install.

npm WARN eslint-config-airbnb@12.0.0 requires a peer of eslint-plugin-import@^1.16.0 but none was installed.
npm WARN eslint-config-airbnb-base@8.0.0 requires a peer of eslint-plugin-import@^1.16.0 but none was installed.

We should roll back eslint-plugin-import in our package.json to a supported version.