adds test case for Archive#toJson(), fixes #73
adds test case for Archive#toJson(), fixes #73

jayendra03/OpenTok-PHP-SDK,jayendra03/OpenTok-PHP-SDK,aoberoi/Opentok-PHP-SDK,aoberoi/Opentok-PHP-SDK,jayendra03/OpenTok-PHP-SDK,opentok/OpenTok-PHP-SDK,aoberoi/Opentok-PHP-SDK,jayendra03/OpenTok-PHP-SDK