Update eslint requirement from ^5.16.0 to ^6.2.1

Updates the requirements on [eslint](https://github.com/eslint/eslint) to permit the latest version.
- [Release notes](https://github.com/eslint/eslint/releases)
- [Changelog](https://github.com/eslint/eslint/blob/master/CHANGELOG.md)
- [Commits](eslint/eslint@v5.16.0...v6.2.1)

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

package.json

@@ -21,7 +21,7 @@
   "devDependencies": {
     "chai": "^4.0.2",
     "coveralls": "^3.0.0",
-    "eslint": "^5.16.0",
+    "eslint": "^6.2.1",
     "istanbul": "^1.1.0-alpha.1",
     "mocha": "^6.1.4",
     "sinon": "^7.3.2"