Proxy support / cURL

On the project I'm currently working on, the way our environment is set up means we need to use a proxy for http requests. Currently the twitter_pull.class.inc file uses drupal_http_request(), where you can't specify a proxy. Not without patching core anyway. See http://drupal.org/node/7881

I'm not necessarily suggesting this is something that needs changing or adding to the module, but case it's of use or interest, I have attached a patch for the twitter_pull.class.inc file which uses cURL to make the request (and thereby allowing us to specify a proxy).