Ffmpeg-normalize

* Fix assignment of audio statistics, fixes 257.

* Warn if dynamic mode is used but linear specified (256)

* Print debug commands in shell-escaped form.

* Allow cover art in MP3.

* Remove warning for short files (87)

* Building on Windows failed due to character conversion (244)

* Docs: add HighMans as a contributor for code (242)

* docs: update README.md

* docs: update .all-contributorsrc

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* Properly handle non-existing input files and skipping.

* Fix: Dockerfile used wrong path.

* Use `https` rather than `http` (238)

* Docs: add psavva as a contributor for code (236)

* docs: update README.md

* docs: update .all-contributorsrc

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* Add Docker support (235)

* Docs: add sian1468 as a contributor.

* Round percentage in test (234)