Patch for file uploads in Windows

I've added a patch to the following ticket to fix file uploading in
Windows. It's a pretty trivial change to explicitly use binary
reads. I've included a test in the patch.

I'd appreciate comments.

Thanks,
Bryan

http://rails.lighthouseapp.com/projects/8994-ruby-on-rails/tickets/1065-multipart_body-truncates-file-in-windows#ticket-1065-4