PHRETS depends on Guzzle, but latest Guzzle causes problems

[acmwallace]

Specifically with the function setDefaultOption:

$this->rets_session->getClient()->setDefaultOption()

This seems to translate down to calling setDefaultOption on a Guzzle client, but somewhere along the line, Guzzle removed that function. This is mainly an issue for me, as I am trying to set up some cookie parameters, and can't. Is there a way to specify a version of guzzle in the dependencies that still contains this function? Or is there another way to set cookie parameters in PHRETS?

[MinaWilliam]

@troydavisson this PR fixes the issue, could you merge it plz? #297