Balance changes

Some balance changes intended not necessarily to make the game easier, but make the difficulty ramp-up feel smoother:

• Reduced damage of Orb, Phantom and Mage enemies, but increased their HP
• Reduced prices of Shard Trader by 500 gold, reduced prices of Shard Smuggler by 1000 gold
• Poison now does flat damage-over-time as opposed to percentage of HP. Burn still takes off a percentage of total HP, but it has been greatly reduced in effectiveness
• Player no longer regenerates HP by default

Will be making more adjustments as more feedback comes in. Thanks for playing!