Add documentation on using proxies

docs/README.md

@@ -15,6 +15,7 @@ here are prose; you might also want to check out the [API documentation][].
 	* [Authenticating your request][authentication]
 * Advanced Usage
 	* [Custom authentication][authentication-custom]
+	* [Requests through proxy][proxy]
 	* [Hooking system][hooks]
 
 [goals]: goals.md
@@ -23,4 +24,5 @@ here are prose; you might also want to check out the [API documentation][].
 [usage-advanced]: usage-advanced.md
 [authentication]: authentication.md
 [authentication-custom]: authentication-custom.md
-[hooks]: hooks.md
+[hooks]: hooks.md
+[proxy]: proxy.md

docs/proxy.md

@@ -0,0 +1,23 @@
+Proxy Support
+=============
+
+You can easily make requests through HTTP proxies.
+
+To make requests through an open proxy, specify the following options:
+
+```php
+$options = array(
+	'proxy' => '127.0.0.1:3128'
+);
+Requests::get('http://httpbin.org/ip', array(), $options);
+```
+
+If your proxy needs you to authenticate, the option will become an array like
+the following:
+
+```php
+$options = array(
+	'proxy' => array( '127.0.0.1:3128', 'my_username', 'my_password' )
+);
+Requests::get('http://httpbin.org/ip', array(), $options);
+```