Look up votes in DB rather than user's session

Issue Summary

Currently, Smackdown stores user votes with each user's session data. This isn't terribly reliable. A more reliable way to determine which smackdowns a user has already voted on is to check the user's votes in the DB.

I've got a patch here that makes the necessary change, but it assumes that only logged-in users can vote. All that has to be added to account for anonymous users is a check for the uid before the DB call to the votingapi_vote table. If it's zero, then search the hostname field for the user's IP address instead of searching for the user's uid.