Minecraft wiki entry for Development_versions, associated text: Tweaked the elder guardian's hitbox.
Modified natural spawn rates for mobs to where they should be (wither skeleton).
Fixed performance issues (FPS drop).
Lots of work on horses.
Tweaked some UI spacing issues.
Tweaked some issues with arrows.
More piston work.
Removed the /clearfixedinv, /setfixedinvslot and /wsserver commands, introduced in build 1.
Now are only for Education Edition.
These commands still can be turned on in files (commands/education.json).
Removed NPC spawn egg.
Version exclusive: Creepers and untamed ocelots now have idle sounds. These were removed (at least for creepers) in a later unknown update.