Handle Login attempts, redirect on success, render Login with error on failure
function attemptLogin(req, res) {
    var username = req.param('username'),
        password = req.param('password'),
        next = req.param('next', '/');

    authdb.validate(username, password, function(err, valid) {
      if (valid) {
        req.session.authed = true;
        req.session.username = username;
        res.redirect(next);
      } else {
        res.emsg = 'Invalid Username or Password';
        render(req, res, 'login.jade', {next: next});
      }
    });
  }