[test_download] Improve playlist handling
[ted] Remove md5sum from test

This failed multiple times, and the md5sum is not that important anyways.
[utils] Modernize tests
[dailymotion] Correct test case
[nhl] Modernize
Move playlist tests to extractors.

From now on, test_download will run these tests. That means we benefit not only from the networking setup in there, but also from the other tests (for example test_all_urls to find problems with _VALID_URLs).
fix up imports
Merge remote-tracking branch 'origin/master'
[extractor/common] Modernize
[veehd] Modernize
release 2014.08.28
[sportdeutschland] Add support for more plain videos
[extractor/common] Correct typo
[test_download] Expect a minimum file size

This should detect when we're downloading a small text file by accident.
[dropbox] Make sure ?dl=0 is ignore (Fixes #3605)
release 2014.08.28.1
[rtlnl] Add support for progressive videos (Closes #3603)
release 2014.08.28.2