Verify that authorize plugin us compatible with the TLS v1.2 changes

[coolbung]

Authorize will stop supporting TLS v1.0 & 1.1 connections in Feb 2018. However let's ensure we're ready already. Although this is really a cURL thing, and as long as hosts use a recent version of curl, we should be good. Let's go ahead and verify this however.

Authorize is also dropping support for the 3DES SSL cipher, so that needs to be verified too.

References -
AuthorizeNet/sdk-php#222
https://blog.pcisecuritystandards.org/migrating-from-ssl-and-early-tls
https://community.developer.authorize.net/t5/The-Authorize-Net-Developer-Blog/Request-for-Comments-API-Best-Practices/ba-p/53668