chore(package): update eslint to version 5.15.3

Closes #10

Author: greenkeeper[bot]

package.json

@@ -32,7 +32,7 @@
   "devDependencies": {
     "ava": "^0.23.0",
     "axios": "^0.17.0",
-    "eslint": "^4.9.0",
+    "eslint": "^5.15.3",
     "eslint-config-standard": "^10.2.1",
     "eslint-plugin-import": "^2.8.0",
     "eslint-plugin-node": "^5.2.0",