chore(package): update eslint to version 6.4.0

Closes #11

Author: greenkeeper[bot]

package.json

@@ -17,7 +17,7 @@
     "use-substate": "0.0.2"
   },
   "devDependencies": {
-    "eslint": "^5.8.0",
+    "eslint": "^6.4.0",
     "eslint-config-airbnb-base": "^13.1.0",
     "eslint-plugin-import": "^2.14.0",
     "husky": "^1.1.2",