/**
  * Constructs a new GitHub tracker instance.
  *
  * @param string $username
  * @param string $password
  * @param string $project
  * @param string $owner Optional project owner, e.g. user or organization.
  */
 public function __construct($username, $password, $project, $owner = null)
 {
     $github = new Client();
     $github->setHeaders(array('Authorization: Basic ' . base64_encode("{$username}:{$password}")));
     $github->authenticate($username, $password, Client::AUTH_HTTP_PASSWORD);
     $this->github = $github->getIssueApi();
     $this->owner = $owner ?: $username;
     $this->project = $project;
 }