Pymediainfo

- Add Mac OS support
- Properly handle files with unicode metadata with Python 3 (23)
- Fix wrong number of argument in calls to a library function (25)
- Fix doc build
- Remove dependency on six

- Take over maintenance from Patrick
- Use the library instead of the CLI binary, makes `MediaInfo.parse()` work on Windows as well
- Use `xml.etree` from Python's stdlib instead of Beautiful Soup; please open an [issue](https://github.com/sbraz/pymediainfo/issues) if you experience regressions
- Fix tests, add one for `MediaInfo.parse()`