0.2.0

• [BREAKING] renamed initialize! to initialize since it's a pure function
• [BREAKING] inputs and outputs for events are now maps containing the keys specified in the :inputs and :outputs vectors
• [BREAKING] event handler functions now must return a map with keys matching the keys specified in the :outputs
• updated the model parser to handle segments without an options map
• introduces :pre and :post conditions
• trigger-events fn added to domino.core, allowing triggering events via ids
• add schema definition validation
• validate for duplicate ids in model