Linkify Github usernames in authors list

- Linkify github usernames
- Remove usernames that do not exist

Change-Id: Ib88b70a3010e915b3570ae5062c8cb416c9a6462
Ok.  Will fix that when I have time.  Just about to leave the office now
and it's a public holiday on Monday.

Might have time during the weekend, otherwise will do it Tuesday.