- Updated version constraints to be much more permissive of what Flutter and SDK versions are accepted.
- Added ValueNotifier so that other interested classes can keep track of what item is displayed on the CoverFlow.
- Added made the builder parameter a named argument [itemBuilder] in keeping with flutter conventions.
- Added [itemCount] field so that users can have a non-infinitely scrolling cover flow. Also adjusted the default viewport value.
- Bumped versioning constraints to support much later versions of Flutter.
- Changed typedef of OnDismissedCallback to return the number of the item called rather than the item itself.
- Initial implementation of simple coverflow.