Upvote button responsiveness

[sydneyitguy]

When you click on upvote button on mobile (or some low latency environment), the button became active 2-3 seconds later.

Users may think the tap just didn’t go thorough so they tap it again, then it will vote and unvote immediately later on.

I guess we need to do it either one of those options

1. Add loading image on button and disable it during the API calls
2. Make the button active immediately first and revoke only if error returned

I think option 2 is better.