Ffsubsync

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* Use rich formatting for Python >= 3.6;
* Use versioneer to manage versions;

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* Fix regression where stdout not used for default output;
* Add ability to specify path to ffmpeg / ffprobe binaries;
* Add ability to overwrite the input / unsynced srt with the --overwrite-input flag;

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* Fix Python 2 compatibility bug;

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* Add --reference-stream option for selecting the stream / track from the video reference to use for speech detection;

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* Remove dependency on scikit-learn;
* Implement PyInstaller / Gooey build process for graphical application on MacOS and Windows;

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* Fix PyPI issues;