code: function findUserFromToken(token, cb) {
    var q = "SELECT * FROM users " +
      "JOIN tokens t ON t.token = $1 " +
      "JOIN users u ON u.id = t.user_id";
  
    db.getClient(function(err, client, done) {
      client.query(q, [token], function(err, r) {
        var result = r && r.rows[0];
        if(!result && !err) { err = new exceptions.NotFound(); }
        if(err) {
          cb(err);
          done(err);
        } else {
          cb(null, result);
          done();
        }
      });
    });
  }
docs: Finds associated user with the token matching `token`
  
  `cb` is passed with the matching user or exceptions.NotFound
  
  @param {String} token
  @param {Function} cb