Upstream changes:

• Add setuptools to install_requires
• Add an option to extract cover_data for libmediainfo ≥ 18.03
• Get version from setuptools_scm

Packaging change:

• Switched source to git, since GitHub tarball doesn't provide necessary information for setuptools_scm, resulting in failed build.

Launched Python interpreter in interactive mode, acquired information about mkv file by means of pymediainfo and checked the output.