Fix Video path being empty even if forced in unittests
Use new is_valid_subtitle method

Thanks to byroot
Fix download method in Podnapisi
Add unittests for Podnapisi
Add unittests for PodnapisiWeb
Update SubsWiki and add unittests
Update Subtitulos and add unittests
Update TheSubDB and add unittests
Update default User-Agent
Unset language_code in PodnapisiWeb
Revamp TVsubtitles

- Use dogpile.cache
- Compute confidence based on votes
- Improved keywords detection
- Add docstrings
- Rename to TVsubtitles
- Add unittests
Update unittests