Bump eslint from 5.3.0 to 6.4.0

Bumps [eslint](https://github.com/eslint/eslint) from 5.3.0 to 6.4.0.
- [Release notes](https://github.com/eslint/eslint/releases)
- [Changelog](https://github.com/eslint/eslint/blob/master/CHANGELOG.md)
- [Commits](eslint/eslint@v5.3.0...v6.4.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

package.json

@@ -93,7 +93,7 @@
     "chai": "^4.1.0",
     "chai-as-promised": "^7.1.1",
     "coveralls": "^3.0.0",
-    "eslint": "^5.3.0",
+    "eslint": "^6.4.0",
     "eslint-config-airbnb-base": "^12.0.1",
     "eslint-plugin-import": "^2.2.0",
     "husky": "^0.14.3",