fix(package): update eslint to version 6.4.0

Closes #147

Author: greenkeeper[bot]

package.json

@@ -38,7 +38,7 @@
     "electron-positioner": "^4.1.0",
     "electron-settings": "^3.1.1",
     "es6-shim": "^0.35.3",
-    "eslint": "^4.3.0",
+    "eslint": "^6.4.0",
     "eslint-plugin-react": "^7.7.0",
     "extend": "^3.0.0",
     "file-loader": "^3.0.1",