This feature has been added to category extension. Now you can change category slug.
https://gist.github.com/rahularyan/0b37680c1a24c1e78baf
Kindly search the site, it has been answered many times.
You can achieve this by hacking core, check here: Vote method, edit this method and just update post meta vote count if user is not logged in.
Try development version of AnsPress from Github.
I will check.