Rebase videos out of repo

[delventhalz]

Move all videos to an external service like YouTube, and then rebase all repo branches to remove these videos from the commit history entirely. The 500MB download is simply too much for students with spotty internet connections.

[delventhalz]

Until 1080p videos are posted to Hyperledger, links to videos here:
https://www.youtube.com/playlist?list=PLW_OuWgJzqX0VDi1OYbbPhToPzdX_6zNd

[delventhalz]

Addressed on personal fork: https://github.com/delventhalz/education-cryptomoji