Bump eslint from 3.19.0 to 4.18.2 (#427)

Bumps [eslint](https://github.com/eslint/eslint) from 3.19.0 to 4.18.2.
- [Release notes](https://github.com/eslint/eslint/releases)
- [Changelog](https://github.com/eslint/eslint/blob/master/CHANGELOG.md)
- [Commits](eslint/eslint@v3.19.0...v4.18.2)

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