Signtool

Added
- added widevine support

Changed
- stop using pefile; verify windows signatures more efficiently

Fixed
- accept the `sha2signcodestub` and `mar_sha384` signing format.
- Fix the missing readme section on the pypi page.

- Bad release: It should have contain the patch in 3.1.1

Fixed
- accept the `macapp` signing format, and translate it to `dmg` for the signing servers.

Changed
- changed the `dmg` signing format to accept and return tarballs.
- changed `unpackfile` to accept `.tgz` and `.tar.gz` suffixes for tarballs.

Removed
- removed the `dmgv2` signing format.