* Removed Python 2 compatibility and testing.
* Refactored to use [Marrow Schema](https://github.com/marrow/schema) for the declarative syntax.
* Full coverage and expanded test capability with improved [Travis-CI](https://travis-ci.org) integration.
* Use of `__assume_interface__` is deprecated; this attribute is now called `__assume__`.
* The ability to define `__doc__` docstrings for each schema element has been removed.
* Wheel distribution.