This update,

Added:
- You can now choose if you want to lose hearts from everything or just players. (anyDeathRemovesHearts in the config.)
- Spectators can be revived from a Reviver. (Player has to be online for it to work.)

Changed:
- Crafting recipe for a Reviver. (See Commands and Crafting Recipes for the current recipe.)

Fixed:
- Reviver bug where if you place a Reviver when you already placed on, it doesn't remove it and it places.
- Heart bug where sometimes, you'll place redstone and not give you a heart.