Fix PodnapisiWeb service

- Remove the sR parameter that does not accept multiple
  values and is case-sensitive
- Ensure the languageId is an integer
- Update filesizes in unittests
Update filesizes in unittests
Skip badly encoded paths and require unicode for api calls
Replace filesizes checks in unittests with subtitles validation

Use pysrt for subtitles validation
Allow empty keywords in services

Applies to addic7ed, subswiki and subtitulos
Fix subtitles validation
Ensure paths are unicode in get_defaults
Remove keywords parameter in PodnapisiWeb as it is not supported
Fix subtitles validation

Subtitles are considered valid if their first 50 lines are
Update unittests for PodnapisiWeb
Fix test_videos by using unicode
Shorten travis install part
Fix subswiki on some movies
New unittests for services using a yaml configuration file
Update requirements

- Add charade and pysrt as test_require
- Add dogpile.cache as install_require
Use dogpile.cache
Update new unittests
Finish list unittests for OpenSubtitles
Add unittests for BierDopje
Use key_mangler to fix the error in dbm backend in dogpile.cache