Update secure travis values
Appraise a user's PRs when they sign a CLA
Rename UnknownCommitter to CommitAuthor

We now track whether or not a commit author has signed a cla using a
flag. This makes it possible to find other commit authors who haven't
signed a CLA on a PR opened by a user who has just signed a CLA.

In the future, we may periodically remove commit authors who have signed
a CLA.