beta/packets: Adjust width of field on 0x35.

Yeah, that definitely needed to be a short, not a byte.
beta: Fix entity equipment packets.

Ugh. Guess it'll be time to delve back into the NBT code soon... :c
Merge Alpha and Beta serializers down into Anvil.

It's not like people actually *use* Alpha worlds, right?
README: Remove hiatus notice.

Pointed out by unknown-d on #mcdevs.
plugins/serializers/beta: Save individual sections.

For Anvil compatibility.
Add an in-memory serializer for testing and mocking.
README: PyPy support is totally there.
beta/structures: Add explicit storage for levels.

This is just the seed, spawn point, and time. No biggie.
world, ibravo: Completely impurify loading from ISerializer.

Objects must now be created in the serializers. This removes a lot of the
pseudo-idempotency from serialization, and permits more flexible serializers
which might store objects instead of serialized data.

Along the way, World stopped being a valid Level, for obvious reasons, so that
had to change as well. That's why this patch is so massive.
plugins/serializers/memory: Update for ISerializer changes.
tests: Use the in-memory serializer.

Faster, cleaner, saner.
utilities/automatic: Fix automaton scanning.
beta/protocol: Fix bad attribute access.
README: I dub thee "Modern!"
geometry/section: Add skylight array to Section.
chunk: Let heightmaps go up to 256.
tests/inventory/test_windows: Fix up a couple tests.
Update docs and comments to indicate serializers.
Use per-section skylights.
beta: Store client settings.

Well, locale and render distance.