chore(package): update eslint to version 5.15.0

Closes #207

Author: greenkeeper[bot]

package.json

@@ -11,7 +11,7 @@
   },
   "devDependencies": {
     "blue-tape": "^1.0.0",
-    "eslint": "^4.7.0",
+    "eslint": "^5.15.0",
     "eslint-config-standard": "^11.0.0",
     "eslint-plugin-import": "^2.3.0",
     "eslint-plugin-node": "^6.0.0",