Add PHP libraries to WordPress

Question

Recently, I needed to add a sftp connection in one of my WordPress template, I found a tutorial which used ssh2 (http://php.net/manual/fr/function.ssh2-sftp.php) but the ssh2 library is not in wp-includes. I found a .tgz file (http://pecl.php.net/package/ssh2), extracted it but all I found was some config files and .phpt files. Is there a simply way to add a PHP library to my WordPress?