The "Count" tag is now required when summoning entities with armor/hand items

In 1.10.2 you were able to use the following command and a Zombie would spawn holding a diamond sword.

/summon Zombie ~ ~ ~ {HandItems:[{id:"diamond_sword"}]}

Now in 16w32a, you have to use the Count tag.

/summon Zombie ~ ~ ~ {HandItems:[{id:"diamond_sword",Count:1}]}

All entities spawned in previous versions will lose their items once upgrading if they don't have the Count tag.