Write characterization tests
Use SimpleCov to check test coverage
Add flog

Manually capture flog output in flog.txt to make it easier to track through the refactoring.
Extract @items[i] to a temporary variable
Extract update
Use each instead of explicit for loop
Remove parens from conditionals
Remove useless semi-colon
Use += and -=
Use -= for odd case
Introduce ItemWrapper delegator
Extract body of update to ItemWrapper
Inline GildedRose#update
Inline item temp
Remove redundant self. qualifiers
Extract increase_quality
Un-nest conditional
Use increase_quality one more time
Swap independent conditions
Extract decrease_quality