Move to using a set instead of a dict when computing e-mail recipients

Review Request #287 — Created March 4, 2008 and submitted

Information

Review Board SVN (deprecated)
trunk

Reviewers

This is some cleanup code from Jonathan Ellis's e-mail patch (http://reviews.review-board.org/r/208/) that moves our e-mail recipient code to using a set instead of a dict.
Unit tests pass.