Update eslint requirement from ^3.19.0 to ^5.3.0 in /{{cookiecutter.app_name}}

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](https://github.com/eslint/eslint/commits/v5.3.0)

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

{{cookiecutter.app_name}}/package.json

@@ -32,7 +32,7 @@
     "babel-preset-env": "^1.6.0",
     "concurrently": "^3.5.0",
     "css-loader": "^1.0.0",
-    "eslint": "^3.19.0",
+    "eslint": "^5.3.0",
     "eslint-config-airbnb-base": "^11.2.0",
     "eslint-plugin-import": "^2.3.0",
     "extract-text-webpack-plugin": "^2.1.2",