chore(electron): update electron to version 3.0.4 to include latest bugfixes. (#228)

https://github.com/electron/electron/releases/tag/v3.0.4

package.json

@@ -17,6 +17,6 @@
   "author": "GitHub",
   "license": "CC0-1.0",
   "devDependencies": {
-    "electron": "^3.0.3"
+    "electron": "^3.0.4"
   }
 }