Ch6 - Create Money superclass and make Dollar its subclass

Chapter 6: Equality for All, Redux, page 28
Ch6 - Generalize Dollar equals implementation

Chapter 6: Equality for All, Redux, pages 28-29
Ch6 - Move Dollar equals implementation to Money

Chapter 6: Equality for All, Redux, page 29
Ch6 - Add tests for Franc equality

Chapter 6: Equality for All, Redux, page 29
Ch6 - Make Franc a subclass of Money

Chapter 6: Equality for All, Redux, page 30
Ch6 - Generalize Franc equals implementation

Chapter 6: Equality for All, Redux, page 30
Ch6 - Remove redundant Franc equals implementation

Chapter 6: Equality for All, Redux, page 31