Viacom URL Services

Reverted them to using the audio codec line in the stream to avoid the
Roku transcoding and edited comment to reflect this. It was my error in
thinking that the audio channel line fixed the issue more accuratetly.
FunnyOrDie - Catch 410 Gone and other http errors
YouTube - Raise exception in case we do not find a fmt_url_map in the page source.
History Channel - Ignore thumbnail if one is not available.
Merge pull request #753 from shopgirl284/viacomfix

Viacom URL Services