chore(package): update eslint to version 6.5.1

Closes #67

Author: greenkeeper[bot]

package.json

@@ -11,7 +11,7 @@
   },
   "devDependencies": {
     "ava": "^0.24.0",
-    "eslint": "^4.0.0",
+    "eslint": "^6.5.1",
     "eslint-config-standard": "^11.0.0",
     "eslint-plugin-import": "^2.2.0",
     "eslint-plugin-node": "^4.2.2",