Update eslint to the latest version 🚀 (#904)

* chore(package): update eslint to version 6.3.0

* chore(package): update lockfile package-lock.json

Author: greenkeeper[bot]

package-lock.json

@@ -53,7 +53,7 @@
     "codecov": "3.5.0",
     "core-js": "3.2.1",
     "cross-env": "5.2.0",
-    "eslint": "6.1.0",
+    "eslint": "6.3.0",
     "eslint-plugin-flowtype": "4.0.0",
     "express": "4.17.1",
     "gulp": "4.0.2",