chore(package): update eslint-config-airbnb to version 18.0.1

Closes #46

Author: greenkeeper[bot]

package.json

@@ -36,7 +36,7 @@
     "body-parser": "^1.18.3",
     "chai": "^4.2.0",
     "eslint": "^5.9.0",
-    "eslint-config-airbnb": "^17.1.0",
+    "eslint-config-airbnb": "^18.0.1",
     "eslint-plugin-import": "^2.14.0",
     "eslint-plugin-jsx-a11y": "^6.1.2",
     "eslint-plugin-react": "^7.11.1",