Use CURL for the https request

`\HTTP_Request2` uses a PHP socket by default, which fails SSL verification due to a CApath not being set for openssl.  It appears the the CApath option must be manually set on ubuntu/debian systems and may vary by operating system.

A fix for this problem has been proposed for php 5.6: https://wiki.php.net/rfc/tls-peer-verification

Until then, we are better off using CURL, because it is build to include a default CApath and will successfully verify the connection.