def post_multipart(url, data, filename, headers = {})
      request(:post, url, headers, {:data => data, :file => filename, :multipart => true})
    end
def post_multipart(url, data, filename, headers = {})
      request(:post, url, headers, {:data => data, :file => filename, :multipart => true})
    end
Uploads the contents of `filename` to the specified `url` using an HTTP POST,
 in combination with given form fields passed in `data`.

 @param url[String] the URL to fetch
 @param data[Hash] hash of the form fields
 @param filename[String] path to the file to be uploaded
 @param headers[Hash] the hash of header keys to values
 @return [Patron::Response]