Update

RaceCarnival
- fixed setRaceContestantFinishTime as was using setStartTime

RaceContestant
- removed validation to check if startTime is before finishTime as is
redundant because finishTime can only be set if after startTime
- updated setCarnival to include validation to check if contestant has
category or not and if so to check that the category exists in the
carnival

Other File
- formatting updates
- object value changes
- some comments added