Tweaking the code sample for 'A Case of Equality'

- removing the 'regular' classes since they result of their comparisons is too easy to get right
- adding a different case class definition that also uses the "problematic" base trait but does not affect case class comparison
Adding a 'DEBUG: ' prefix to SpyOnEquals
CCD -> CCSpy
Updated candidate answers

- 'true, true, false, false' -> 'false, true, false, true'
i.e. mixing in SpyOnEquals at declaration or instanation time *both* "break" equals
Aligning explanation with new candidate answers