Gotta love mojang..
This update is using skin blobs and uuid lookups to grab the skins of offline players.
Basically. They re-enabled skins on players. With a little more functionality.
I would add support for disguising the players with other skins. But its extremely likely that it will be broken within 2 months.

Basically.

This works on 1.7.9. I'm not supporting 1.7.6 - 1.7.8.