chore(package): update eslint-config-airbnb to version 18.1.0

Closes #11

Author: greenkeeper[bot]

package.json

@@ -39,7 +39,7 @@
     "chai": "^4.2.0",
     "coveralls": "^3.0.2",
     "eslint": "^5.11.1",
-    "eslint-config-airbnb": "^17.1.0",
+    "eslint-config-airbnb": "^18.1.0",
     "eslint-config-airbnb-base": "^13.1.0",
     "eslint-plugin-import": "^2.7.0",
     "eslint-plugin-jsx-a11y": "^6.0.2",