@jcrivera I'm not clear as to how exactly this was broken, or how this fixes it.  The comment here:

https://github.com/nicksieger/multipart-post/blob/abb54501ecb43e554723c9fa2a814a19b6348bbe/lib/composite_io.rb#L56-L62

Implies to me that it is valid as is, but if we were to update it, would be something along the lines of 

```Upload.new(file_io, , "text/plain", binary_data)```  and would only be used if a file handler already existed and was open for this file