Improve parsing for email addresses like: alincoln <alincoln at logcabin dot com>

Summary: There are some of these in the Mercurial repository commit log. Handle them more gracefully, without raising warnings.

Test Plan: Ran unit tests.

Reviewers: btrahan, vrana

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D2592