CYB-377 Youtube URLs are not always https

* changed the regular expression where it matched the protocol to always match
    http:// or https://
* This will ensure that Youtube videos are handled as such.

[CYB-377 Youtube URLs are not always https](https://jira.ets.berkeley.edu/jira/browse/CYB-377)
I think this should be 2 spaces instead of 4. I'll fix this up when I merge