Torsional friction video is missing

[scpeters]

The link to the YouTube video in the Torsional Friction tutorial is broken:

https://github.com/osrf/gazebo_tutorials/blame/master/torsional_friction/tutorial.md#L187

https://www.youtube.com/embed/LveVKwiXlx0

http://gazebosim.org/tutorials?tut=torsional_friction&cat=physics

We should probably make a new video from the example world.

[chapulina]

I wonder what channel that was on.

I think a gif is easier to maintain than a video.