[extractor/common] Document ie_key in url results
[extractor/common] Add generic SMIL formats extraction routine
[bet] Add extractor (Closes #4416)
Fix PEP8 issue E713
release 2014.12.10
[youtube] Handle missing DASH manifest (Fixes #4421, fixes #4420)
release 2014.12.10.1
[youtube] Pass in all variables to DASH manifest (Fixes #4424)
release 2014.12.10.2
[facebook] Make thumbnail and duration optional

Fixes #4425.
Looks like both properties aren't given to us anymore. For now, just fall back to not returning them.
release 2014.12.10.3
[smotri:broadcast] Fix extraction