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Changes since Pluggy:
* Made everything asynchronous.
* Removed deprecated code, including the legacy ``__multicall__`` parameter
handling.
* Renamed from **pluggy** to **aiopluggy**
* Removed compatibility with Python versions before 3.5.
* Updated documentation.
* Stripped much of the original CI stuff (tox, travis-ci) because I was in a
hurry to get some MVP running. Will probably be re-introduced later.
* Stripped some of the less-frequently used parts of the API, including:
* the many hook-2-plugin, plugin-2-name, name-2-plugin, plugin-2-hooks
translators in `PluginManager`;
* plugin unloading.