chore(package): update eslint-config-airbnb to version 18.0.0

Closes #204

Author: greenkeeper[bot]

package.json

@@ -66,7 +66,7 @@
     "chai": "^3.5.0",
     "codecov": "^2.2.0",
     "eslint": "^3.19.0",
-    "eslint-config-airbnb": "^15.0.1",
+    "eslint-config-airbnb": "^18.0.0",
     "eslint-config-mcs-lite": "^0.4.0",
     "eslint-config-prettier": "^2.1.1",
     "eslint-plugin-import": "^2.2.0",