chore(package): update eslint to version 5.15.2

Closes #53

Author: greenkeeper[bot]

package.json

@@ -24,7 +24,7 @@
   "devDependencies": {
     "babel-eslint": "^8.2.2",
     "chai": "^4.1.2",
-    "eslint": "^4.7.2",
+    "eslint": "^5.15.2",
     "mocha-eslint": "^4.1.0",
     "supertest": "^3.0.0"
   },