chore(package): update eslint to version 6.4.0

Closes #34

Author: greenkeeper[bot]

package.json

@@ -35,7 +35,7 @@
     "babel-plugin-transform-react-jsx": "^6.24.1",
     "babel-preset-es2015": "^6.24.1",
     "babel-register": "^6.24.1",
-    "eslint": "^4.1.0",
+    "eslint": "^6.4.0",
     "istanbul": "^0.4.5",
     "jsdom": "^11.0.0",
     "mocha": "^5.0.0",