Authentication for Private Endpoints using Guzzle?

Has anyone been able to successfully implement this using Guzzle 6 and make authenticated API calls? I've been attempting this but I'm struggling to troubleshoot what's not working. It seems like cookies are not being sent with my request (which would be why it always says I need to login). Is anyone familiar, willing, and able to take a look? http://pastebin.com/nJxntB0T