Merge pull request #2456 from AGSPhoenix/master

[YT] Fix incorrect format code descriptions
[testurl] Fix case when only one IE matches
[vevo] Add suppot for v3 SMIL URLs (Fixes #2409)
[vevo] Add age_limit support
release 2014.02.25.1
Skip youtube toptracks test

All the playlists return 500 errors.
[crunchyroll] Tidy and modernize
[crunchyroll] Fix subtitle lang code extraction
[crunchyroll] Handle error message
[crunchyroll] Use `enumerate`
Add thumbnail for metacafe
Add support for ocw.mit.edu video lectures
Update __init__.py
Extract thumbnail with _og_search_thumbnail
[nbc] Add an extractor for the main nbc.com site

Some of the videos are encrypted, the f4m downloader doesn’t support them.
Merge pull request #2461 from niebles/master

Update __init__.py

`io` wasn't imported.
[mixcloud] Fix _VALID_RE (fixes #2462)

Accept any character except `/` for uploader and the name, caused problems with non ASCII characters
[mit] Modernize
Merge branch 'master' of github.com:rg3/youtube-dl
Merge branch 'ocw-mit-edu' of https://github.com/amlweems/youtube-dl