code: function getUser(username, done) {
    return getModels(function(m) {
      return m.collections.user.findOne({ username })
        .populate("tokens")
        .populate("groups")
        .populate("leading")
        .exec(done);
    });
  }
docs: Get a single user. Automatically loads the tokens.
  
  @param {String} username
  @param {Function} done - done(err, user)