After loading the latest snapshot, all advancements were reset.  Also my skin reverted to the default Steve.

What I expected to happen was...:

I would load the update and check out the new content without losing any of my existing progress or settings.

What actually happened was...:
I noticed that I was getting beginner advancements after I was very far into the game.  I then checked my advancements and noticed that they were all gone.  I also noticed that my arm texture was wrong, so then I checked and my whole appearance reverted back to the starting Steve appearance.

Steps to Reproduce:
1. No steps other than running the new update.