v0.3: A Bene Placito

Another few months, another few commits! Making serious progress, yo.

Changes:

• Fix pages not updating after refresh sometimes
• Fix thumbnails on /3/
• Handle WebM hover/expansion if that ever becomes a thing.
• Correctly classify mistyped captcha errors, and stop
  removal of post text for other failures (duplicate file, etc)

Known issues:

• Sometimes backlinks/forwardlinks will get duplicated after updates. I haven't figured out
  in what circumstances this occurs, so if you see it, take a screenshot and report, please.
• Posting UX is still generally inferior to anything else, including the native extension. This will be fixed Soon™