Fix drop ratios

Ratios left intact as commented in algos.coffee.  

But this means that potion drop odds are as follows:  

Gold:  10% 
CC Pink, CC Blue, Zombie: 6.66% each (6.66 * 3 = 20% total chance)
Red, Shade, Skeleton:  10% each ( * 3 = 30%) 
Base, White, Desert:  13.33% each ( * 3 = 40%)

Suggest (with mixed feelings) reducing Very Rare to 4% and distributing the other 6% between other three tiers.  Will write & submit that patch too; pick your -poison- potion!