Description:
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One feature I noticed to be missing from the 1.0 release is support for multipart form post requests.  This is required for updating your background image or logo using the twitter api.  It seems that Twitter is pointing people to this example in ruby that works: http://mehack.com/uploading-a-background-image-to-twitter-using

So following this convention, we'd need to check for parameter names beginning with an @ symbol (see the example in the reproduce code section below).  Those parameters would not be included in the signature.  The php curl extension automatically imports the data for a parameter value that contains a filename preceded by an @ symbol.  We'd also have to do something similar here and set the CURLOPT_HTTPPOST option.

There's a php implementation over here http://github.com/jmathai/twitter-async/blob/master/EpiOAuth.php  Look at the isMultipart, prepareParameters, and httpPost methods in particular.

My apologies in advance if this isn't the correct place to report this.  I didn't see a discussion group for this extension where I could ask about it first.  I love to see this extension continue to be the "de facto standard" - so I hope we can get this feature added.  I'm sure the Twitter API isn't the only one that needs it (I saw mention on a dropbox.com discussion, at least - http://forums.dropbox.com/topic.php?id=19771).

Reproduce code:
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// assumptions:
//     - $oauth is an instance of OAuth with access token configured
//     - /home/me/bg.jpg is the background image file on the local filesystem

$oauth->fetch('http://api.twitter.com/1/account/update_profile_background_image.json', array('@image' => '@/home/me/bg.jpg'), OAUTH_HTTP_METHOD_POST);

// expected result: file data is posted using multipart/formdata, 
// a 20x response code is returned from twitter, 
// and the background image is updated


Expected result:
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Expecting that the file data is posted using multipart/formdata, a 20x response code is returned from twitter, and the background image is updated for the twitter account.

Actual result:
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Currently, doing this results in a request with
Content-Type: application/x-www-form-urlencoded %40image=%40%2Fhome%2Fme%2Fbg.jpg