Release 3.0.0 adds several major features: 1. full support for C++11 2. a compact optional type. 3. Support for adapting enums not defined by the wise enum macro API. 4. Support for enums nested in classes. It's a breaking change because: 1. I slightly changed the interface surrounding fixed storage enums 2. I also slightly changed how the defaults for string and optional types work between 14 and 17. 3. Changed the macro names to override the types slightly. All very minor changes, but still breaking.