Disable youtube recommendations at end of video

Hi Nick,

we're quite happily using AESOP in a few of our projects, along with a few small and some more or less intrusive modifications.

I'll start to clean up and package pull requests for the changes I think a greater user base would benefit from - you're free to ignore them, of course, but if you merge them, the update process for us will become easier :)
Here's the first one of more to come:

Normally, the embedded youtube player will show recommended videos based
on the one played.
This isn't however desired if we want the reader to submerge into a
long, distraction-free reading/viewing experience, so we've disabled the
video recommendations for our projects. I even think this would make a
good default for AESOP.

Thank you,
Artjom