v0.3.3

Added

• Full support for closed-set types (Literal from typing and classical Enum)
• Constraint type OneOf (for both Literal and Enum representation after parsing,
  but can be used as part of real model)
• Violation strategy NOT_ALLOWED_VALUE for generating values outside allowed sets
• Early validation for
  • empty Literal and Enum
  • invalid constraint combinations with closed-set types

Changed

• Oneof (closed-set types) is now treated as independent terminal constraint.
  Combinig Literal/Enum with other constraints results in a parsing error.