Possibly fixed a problem with JSON in Safari/Mac.
Users can now vote once on their own content.

Legacy table is not dropped for the time being, as I intend to get a proper upgrade path as to not lose the old votes from first branch.
The module now degrades gracefully without JavaScript (works without JavaScript).
Anonymous users voting is optional (when enabled, it works).

See the tutorial behind this project at: http://11heavens.com/using-ajax-in-Drupal-6