Bump eslint from 4.19.1 to 5.15.1

Bumps [eslint](https://github.com/eslint/eslint) from 4.19.1 to 5.15.1.
- [Release notes](https://github.com/eslint/eslint/releases)
- [Changelog](https://github.com/eslint/eslint/blob/master/CHANGELOG.md)
- [Commits](https://github.com/eslint/eslint/compare/v4.19.1...v5.15.1)

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

package.json

@@ -32,7 +32,7 @@
     "babel-preset-stage-2": "^6.24.1",
     "babel-preset-stage-3": "^6.24.1",
     "clean-css": "^4.1.9",
-    "eslint": "^4.10.0",
+    "eslint": "^5.15.1",
     "eslint-config-postcss": "^2.0.2",
     "eslint-config-prettier": "^2.7.0",
     "eslint-plugin-prettier": "^2.3.1",