Problems installing Vokuro using Composer

As I attempt to download Vokuro's vendor dependencies with Composer, I get the following error message:

C:\xampp\htdocs\vokuro-master>composer install
Loading composer repositories with package information
Updating dependencies (including require-dev)
  - Installing swiftmailer/swiftmailer (v5.4.3)
    Loading from cache

  - Installing amazonwebservices/aws-sdk-for-php (1.6.3)
    Loading from cache

amazonwebservices/aws-sdk-for-php suggests installing aws/aws-sdk-php (You should consider upgrading to version 2 of the AWS SDK for PHP)
Package amazonwebservices/aws-sdk-for-php is abandoned, you should avoid using it. Use aws/aws-sdk-php instead.
Writing lock file
Generating autoload files

And then, attempting to use the Sign Up form (/session/signup) gives the following error:

Expected response code 250 but got code "530", with message "530-5.5.1 Authentication Required. Learn more at 530 5.5.1 https://support.google.com/mail/answer/14257 h7sm23504892wjd.17 - gsmtp "
#0 C:\xampp\htdocs\vokuro-master\vendor\swiftmailer\swiftmailer\lib\classes\Swift\Transport\AbstractSmtpTransport.php(281): Swift_Transport_AbstractSmtpTransport->_assertResponseCode('530-5.5.1 Authe...', Array)
#1 C:\xampp\htdocs\vokuro-master\vendor\swiftmailer\swiftmailer\lib\classes\Swift\Transport\EsmtpTransport.php(270): Swift_Transport_AbstractSmtpTransport->executeCommand('MAIL FROM:<phos...', Array, Array)
#2 C:\xampp\htdocs\vokuro-master\vendor\swiftmailer\swiftmailer\lib\classes\Swift\Transport\EsmtpTransport.php(349): Swift_Transport_EsmtpTransport->executeCommand('MAIL FROM:<phos...', Array)
#3 C:\xampp\htdocs\vokuro-master\vendor\swiftmailer\swiftmailer\lib\classes\Swift\Transport\AbstractSmtpTransport.php(416): Swift_Transport_EsmtpTransport->_doMailFromCommand('[email protected]')
#4 C:\xampp\htdocs\vokuro-master\vendor\swiftmailer\swiftmailer\lib\classes\Swift\Transport\AbstractSmtpTransport.php(444): Swift_Transport_AbstractSmtpTransport->_doMailTransaction(Object(Swift_Message), '[email protected]', Array, Array)
#5 C:\xampp\htdocs\vokuro-master\vendor\swiftmailer\swiftmailer\lib\classes\Swift\Transport\AbstractSmtpTransport.php(176): Swift_Transport_AbstractSmtpTransport->_sendTo(Object(Swift_Message), '[email protected]', Array, Array)
#6 C:\xampp\htdocs\vokuro-master\vendor\swiftmailer\swiftmailer\lib\classes\Swift\Mailer.php(85): Swift_Transport_AbstractSmtpTransport->send(Object(Swift_Message), Array)
#7 C:\xampp\htdocs\vokuro-master\app\library\Mail\Mail.php(117): Swift_Mailer->send(Object(Swift_Message))
#8 C:\xampp\htdocs\vokuro-master\app\models\EmailConfirmations.php(76): Vokuro\Mail\Mail->send(Array, 'Please confirm ...', 'confirmation', Array)
#9 [internal function]: Vokuro\Models\EmailConfirmations->afterCreate()
#10 [internal function]: Phalcon\Mvc\Model->fireEvent('afterCreate')
#11 [internal function]: Phalcon\Mvc\Model->_postSave(true, false)
#12 C:\xampp\htdocs\vokuro-master\app\models\Users.php(112): Phalcon\Mvc\Model->save()
#13 [internal function]: Vokuro\Models\Users->afterSave()
#14 [internal function]: Phalcon\Mvc\Model->fireEvent('afterSave')
#15 C:\xampp\htdocs\vokuro-master\app\controllers\SessionController.php(48): Phalcon\Mvc\Model->save()
#16 [internal function]: Vokuro\Controllers\SessionController->signupAction()
#17 [internal function]: Phalcon\Dispatcher->callActionMethod(Object(Vokuro\Controllers\SessionController), 'signupAction', Array)
#18 [internal function]: Phalcon\Dispatcher->_dispatch()
#19 [internal function]: Phalcon\Dispatcher->dispatch()
#20 C:\xampp\htdocs\vokuro-master\public\index.php(41): Phalcon\Mvc\Application->handle()
#21 {main}