README contains dead link to introduction video

[cst0]

Hi, just wanted to let you know that the video in the README seems to be private, breaking the link on both this README and the ROS wiki.

[MatthijsBurgh]

@jelfring @svddries do you know who the owner of that video is?

(The videos in the tutorials are still available)

[jelfring]

Looks like I own the tutorial videos, but not the main one. I guess @svddries owns the one that is missing...