Add Support for Requests' SSL Cert Verification Options

* Add option to specify cert file(s)
* Add option to ignore verifying the SSL certificate
* Add option to suppress warning issued by urllib3 when SSL verification is ignored.

[requests ssl verification](http://docs.python-requests.org/en/latest/user/advanced/#ssl-cert-verification)
[urllib3 insecure warnings](https://urllib3.readthedocs.org/en/latest/security.html#insecurerequestwarning)