changed mod race contestant + tests

- Discovered that when modifying existing customer with the "team of 3"
TreeMap, it actually added a new entry as the key was different
(familyName,givenName,id), whereas the other TreeMap was just based on
id.
- Also discovered that if you modified the id-based TreeMap with a
contestant that had a different id, the Key and id would be different.
Should be the same to ensure that searches on id actually get the
RaceContestant you want.
- Changed validation to ensure mod can only be made when the id's are
the same for both old and new RaceContestant,
- created a local copy of the old RaceContestant to return, rather than
directly via put method.
- deleted both old contestants from TreeMaps first, then added new
Contestants to ensure same id as part of key for both TreeMaps.
output file