Implement Prop Validation

https://facebook.github.io/react/docs/reusable-components.html

For instance if I don't pass in `states` or `transitions` it should be validated.

Start with the linked React reusable-components documentation, then trace where the `states` and `transitions` props enter the library. Define the expected behavior for missing props and verify that invalid or absent values produce the intended validation feedback.

Written by the indexing model from the issue text.