Jetpack activation, fix register_http_request_failed error

Fix "Jetpack could not contact WordPress.com: register_http_request_failed. This usually means something is incorrectly configured on your web host." in just a few steps, and you are to able to connect the Jetpack plugin activation:

1. download the cacert.pem file (http://curl.haxx.se/ca/cacert.pem) to your computer
2. upload cacert.pem to your website, preferably to an unwritable location (but readable for the web server, just to protect the file)
3. download and open the wp-includes/class-http.php file
4. somewhere around line 1084, within function request() of class WP_Http_Curl{}, add:
   curl_setopt( $handle, CURLOPT_CAINFO, "/path/to/domain/cacert.pem" );
5. save and upload the file to the wp-includes/ folder