Clarify that download rate is in bytes per second

I found https://github.com/rg3/youtube-dl/commit/f918ec7ea29a37521d1fc22fb9f900283c5a2c49 but it is still not clear to anyone who hasn't read Issue #723 whether the limit is in bits or bytes.  This is doubly confusing because 1) ISPs usually advertise speeds in bits per second, and 2) lowercase "k" and "m" are often used in correlation with bits rather than bytes.
Extractor for websurg.com
Merge remote-tracking branch 'upstream/master' into websurg
Improvements
Changes suggested by @phihag
Unused variable
Use self._download_webpage everywhere
[FlickrIE] Fix HTTPS url
Merge pull request #1551 from rzhxeo/flickr

[FlickrIE] Fix HTTPS url
[ted] Prepare #980 merge
Document formats (for #980)
Clarify that url and ext are optional when formats is given (#980)
[mtv] Prepare for #980
[comedycentral] Prepare for generic video extraction (#980)
Merge remote-tracking branch 'origin/master'
[francetv] Use common format for ID of generation-quoi subextractor
[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