chore(package): update eslint to version 6.2.1

Closes #15

Author: greenkeeper[bot]

package.json

@@ -29,7 +29,7 @@
   "devDependencies": {
     "assert-dotenv": "^3.0.0",
     "coveralls": "^3.0.2",
-    "eslint": "^5.4.0",
+    "eslint": "^6.2.1",
     "eslint-config-prettier": "^3.0.1",
     "eslint-config-xo": "^0.24.2",
     "eslint-plugin-json": "^1.2.1",