Fedsim

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* added fedsim.scores which wraps torch loss functions and sklearn scores
* moved reporting mechanism of distributed algorithm for supporting auto monitor
* added AppendixAggregator which is used to hold metric scores and report final results
* apply a patch for wrong pypi supported python versions

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* First major pre-release.
* The package is restructured
* docs is updated and checked to pass through tox steps

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* Fourth release on PyPI.