- Instructed Maven to use UTF-8 encoding
- Added README with instructions for playing the game
- Removed UML diagrams that are not relevant to SOFT 160 assignment

mostCommonFace() now returns an int (vs an Optional<Integer>)

Since almost all of yatzy's scoring is based on sums of die faces,
we can simply get the satisfying dice and add their faces. The only
special case is scoring Yatzy.

- TwoPairCategory and FullHouseCategory replaced with OfTwoKindsCategory
  - changed scoring as well
  - original categories remain for now until they're replaced in the
    production code

- NumberCategory preserved
- ChanceCategory preserved
- InARowCategory replaced with SequenceCategory, which has different
  satisfaction rules and different scoring rules

- renamed package from yoctsee to yatzy
- removed sandbox