download-file

Would it be possible to have an option to make Downloader pre-allocate the final file and stream into it directly instead of using temporary files? With large downloads the moving of temp files into the final file can take some time, especially with an overzealous anti-virus program.

The write function for download currently downloads each part to a temporary file on the disk and then joins them to create the final file. However, it would be much more efficient to do this in memory. I.E writing to a object instead of a file. We would then join all these chunks to create the final file.

An example of this in C can be seen [here](https://curl.haxx.se/libcurl/c/getinmemory.htm