[rtlnow] Skip test on travis
[yahoo] Do not try to run rtmpdump on travis
Include length in player cache ID

Some videos use the same player with IDs of multiple lengths.
See https://travis-ci.org/rg3/youtube-dl/jobs/12126506#L319 for an example.
[jeuxvideo] fix video file md5sum
[redtube] pep8
[yahoo] Fix test title
[yahoo] Switch ext of test