Don't require Github fake email addresses in .authors.yml

[takluyver]

Users who tick the "Keep my email addresses private" setting on Github have commits from the web interface associated with an email address <numbers>+<username>@users.noreply.github.com (e.g. 327925+takluyver). They can also use this for commits to avoid recording their real email address.

It would be nice if these 'email addresses' were associated with authors by the github: takluyver field in .authors.yml, rather than pushing people to copy them into the YAML.