Add PHP 7.3 and SilverStripe 4.3 to Travis builds
Add PHP 7.3 and SilverStripe 4.3 to Travis builds

nyeholt/silverstripe-queuedjobs,silverstripe-australia/silverstripe-queuedjobs,andrewandante/silverstripe-queuedjobs,silverstripe-australia/silverstripe-queuedjobs,andrewandante/silverstripe-queuedjobs,nyeholt/silverstripe-queuedjobs