chore(package): update eslint to version 6.4.0

Closes #35

Author: greenkeeper[bot]

package.json

@@ -50,7 +50,7 @@
     "css-loader": "^2.0.0",
     "enzyme": "^3.7.0",
     "enzyme-adapter-react-16": "^1.6.0",
-    "eslint": "^5.6.1",
+    "eslint": "^6.4.0",
     "eslint-config-react-app": "^4.0.0",
     "eslint-loader": "2.1.2",
     "eslint-plugin-flowtype": "^3.9.1",