Fixed:

• Apply MaxStackSize to the player's inventory when using Player#addItem, so now instead of 99 items popping up in the inventory if giving 99 keys or any items, it'll split 64/35
  • Spigot for some odd reason made Player#addItem use the max stack size for the inventories. #hardforkwhen

Changes:

• Moved i/o operations off the main thread.
• Cleaned up build script.