Release Candidate 3: More difficult enemies, but also hearts

Changes since RC2:

• Fixed a silly bug that allowed a treasure chest spawning in a room to clear an adjacent room if the player left too quickly
  
  • Sorry speedrunners!
• All enemies have a small chance to drop a small heart, which heals 2 damage (one full heart)
  • These will only drop if the player is not already at max health
  • Slimes have a higher chance than other mobs to drop hearts
• Enemies now have variable behavior rather than just health pools, based on their "difficulty" (palette):
  • Zombies and Spiders chase the player more quickly
  • Advanced Moles throw wrenches faster, and remain vulnerable for a shorter amount of time

It's feeling more like a finished game, but there's still 6 hours to go, and I have coffee.