[TeacherTubeIE] Add extractor for teachertube.com videos + classrooms (fixes #3046)
[naver] Add rtmp formats (fixes #3054)
[naver] Modernize
[xvideos] Capture and output inline error if any
[xvideos] Replace test
Merge remote-tracking branch 'pulpe/tagesschau'
[teachingchannel] Add extractor (closes #3048)
[test/test_youtube_lists] Replace mix list

The old video doesn't have a mix anymore.
[Youtube] Add format code 271 (1440p webm)
Merge pull request #3057 from pulpe/yt_fmt

[Youtube] Add format code 271 (1440p webm)
[tagesschau] Add support for width/height
Merge branch 'master' of github.com:rg3/youtube-dl

Conflicts:
	youtube_dl/extractor/__init__.py
Merge remote-tracking branch 'pulpe/teachertube'

Conflicts:
	youtube_dl/extractor/__init__.py
Merge remote-tracking branch 'georgjaehnig/spiegeltv'
[teachertube] Add support for audios
[spiegeltv] Simplify and PEP8
[cnn] Improve thumbnail extraction
Credit @georgjaehnig for spiegeltv
Merge branch 'master' of github.com:rg3/youtube-dl
[ku6] Add new extractor