CLOSED - task 15: 例外設計の見直しが必要 
http://github.com/kazyury/MementoWeaver/issues/issue/15
ScanProcessor#findMemento was moved to MementoDao(changed
responsibility).
CLOSED - task 16: tag-category(memento)-generator-subgenerator関係の整理 
http://github.com/kazyury/MementoWeaver/issues/issue/16