Update README.md - Proxy support

Proxy support documentation

README.md

@@ -491,6 +491,7 @@ var accessToken = FB.options('accessToken'); //will get the accessToken of 'XYZ'
 The existing options are:
 * `'accessToken'` string representing the facebook accessToken to be used for requests. This is the same option that is updated by the `setAccessToken` and `getAccessToken` methods.
 * `'appSecret'` string representing the facebook application secret.
+* `'proxy'` string representing an HTTP proxy to be used. Support proxy Auth with Basic Auth, embedding the auth info in the uri: 'http://[username:password@]proxy[:port]' (parameters in brackets are optional).
 * `'timeout'` integer number of milliseconds to wait for a response. Requests that have not received a response in *X* ms. If set to null or 0 no timeout will exist. On timeout an error object will be returned to the api callback with the error code of `'ETIMEDOUT'` (example below).
 
 `'scope'` and `'redirectUri'` have been whitelisted in options for convenience. These value will not be automatically