chore(package): update eslint to version 6.3.0

Closes #29

Author: greenkeeper[bot]

package.json

@@ -44,7 +44,7 @@
   "devDependencies": {
     "babel-cli": "6.26.0",
     "babel-preset-env": "1.7.0",
-    "eslint": "^5.3.0",
+    "eslint": "^6.3.0",
     "eslint-config-prettier": "^3.0.0",
     "eslint-plugin-prettier": "^2.6.2",
     "greenkeeper-lockfile": "1.15.1",