Add Item#aged_brie?, Item#backstage_passes? and Item#sulfuras?
Add Item#decrement_quality
Add Item#increment_method
Add Item#reset_quality
Formatting
Add Item#decrement_sell_in
Start untangling the logic
Finish untangling the logic
Move logic to Item#update_quality
Add Item.from
Move Aged Brie logic into AgedBrieItem
Move Backstage Passes logic into BackstagePassesItem
Finish splitting the logic into the different *Item classes