Forgot that enums can't be declared static
Updated .csproj file
Updated Hand.CompareTo to use new Hand.Score signature
Refactored Hand.IsStraightFlush() to use foreach loop
Implemented Hand.IsFourOfAKind()
Fixed Hand.IsFourOfAKind - forgot what it meant
Made IsFourOfAKind make more sense with better variable names
Implemented Hand.IsFullHouse()