rawurlencode string to sign

I've been trying to use the SDK to create pre signed urls to upload directly to S3 but every request has resulted in a 403 forbidden response.

I have been able to get this working by creating the signatures myself using the method described here http://www.ioncannon.net/programming/1539/ The only difference is that the string is being encoded. 

After making the change to my local SDK the pre-signed urls now work.