Add documentation on using SSL parameters

docs/usage-advanced.md

@@ -0,0 +1,40 @@
+Advanced Usage
+==============
+
+Secure Requests with SSL
+------------------------
+By default, HTTPS requests will use the most secure options available:
+
+```php
+$response = Requests::get('https://httpbin.org/');
+```
+
+Requests bundles certificates from the [Mozilla certificate authority list][],
+which is the same list of root certificates used in most browsers. If you're
+accessing sites with certificates from other CAs, or self-signed certificates,
+you can point Requests to a custom CA list in PEM form (the same format
+accepted by cURL and OpenSSL):
+
+```php
+$options = array(
+	'verify' => '/path/to/cacert.pem'
+);
+$response = Requests::get('https://httpbin.org/', array(), $options);
+```
+
+Alternatively, if you want to disable verification completely, this is possible
+with `'verify' => false`, but note that this is extremely insecure and should be
+avoided.
+
+## Compatibility Note
+Requests supports SSL across both cURL and fsockopen in a transparent manner.
+Using fsockopen is slightly less secure, as the common name in certificates is
+not checked. This is due to
+[PHP lacking support for Subject Alternate Name][php-bug-47030]
+(and OpenSSL also [lacking the low-level support][php-bug-55820] in PHP). If
+these bugs are fixed, support for common name checking will be enabled by
+default.
+
+[Mozilla certificate authority list]: http://www.mozilla.org/projects/security/certs/
+[php-bug-47030]: https://bugs.php.net/bug.php?id=47030
+[php-bug-55820]:https://bugs.php.net/bug.php?id=55820