Remove manifest.in - Githubissues

MANIFEST.in's are outdated and can safely be deleted without any other change.

CHANGELOG.md is redundant since the description already includes that information
The CONTRIBUTING.md file doesn't exist
The test directory shouldn't be included because it does nothing for the user and adds 3.2M of unneeded storage space
setup.cfg, README.md, and LICENSE are automatically added during packaging

slhck / ffmpeg-normalize