Skip f4m, doesn't work (yet); correctly extract m3u8, and prefer plain HTTP files.
Thanks to https://blog.fefe.de/?ts=a577685d for pointing out support is missing.
ttml is now served instead of srt
Now all _extract_*_formats routines return a list
Deletes parse_xml from utils, because it also does it.
This is now implemented generic in YoutubeDL.urlopen
I cannot reproduce this error, it's from travis.