Version 2.0.0

This release introduces the concept of type representatives (#180). fantasy-land/empty, fantasy-land/of, and fantasy-land/chainRec must now be defined on type representatives. It's no longer necessary to look for definitions in two places – expressions such as typeof x['fantasy-land/empty'] == 'function' ? x : x.constructor are no longer required when defining polymorphic functions!

The type-class diagram in the readme now includes all the type classes defined in the specification (#192).