Include an explicit author when committing.

Include an explicit author when committing.

Committed: https://code.google.com/p/dart/source/detail?r=14049

[Bob Nystrom, 2012-10-24 23:38:36]

"git commit" will fail if you don't have a user and email in your git config (or
git can't successfully infer it from /etc/passwd or elsewhere).

Generally, we don't commit in pub, so that's fine, but the *test* code for pub
does: it commits to its little fake repos.

So this just adds an explicit author there.

[nweiz, 2012-10-24 23:40:30]

lgtm