Cleanup & Updates

- Updated readme.
- Removed ChallengeRatingCalculator.java.
- Updated DiceBag.java to reflect changes elsewhere.
- Renamed EncounterLevelCalculator to EncounterCalculator.
- UpdatedCombatTracker.java to reflect changes elsewhere.
- Fixed constructor in PointBuyCalculator.java.
- Reversed If/Else cases in Creature35E.compareTo method.