also ensure it is valid for linux.

- bugfix: on windows use rd command instead of rm command.
- bugfix: do not rewrite m3u8 file (again) if local file is reused.
- minor, adjust some log message level.

it needs the m3u8 media playlist url in order to do proper rewriting.

previously absolute path may not be replaced with relative path if there is no
http or query param.

include utils/versionutils.py and requirements.txt in MANIFEST.in

use action=version for --version support, this allow me to make -o and
URL required params.

this allow user to config download worker poolsize.

honor $XDG_CACHE_HOME,
uses %LOCALAPPDATA% on windows.

support relative link in fragment url

also changed ffmpeg log level to warning.

enabled git pre-commit hook to catch such errors.

moved default temp dir to ~/.cache/