Upgrade americano version and handle file uploads with streams

I use multiparty middleware to handle file uploads. I use streams instead of saving file to the disk before storing it in the Data System. 

The PR is not ready to merge but I think most of the code can be reviewed.

What needs to be done:
- fix tests (after all in files failed and folder tests kept stuck).
- test if it works with the current version of the Data System (I only tested it with the Data System with upload managed via stream (see my other PR https://github.com/cozy/cozy-data-system/pull/88)

Can you add a comment here to tell it's mandatory to append the file at last? I'm aware of that just because I encountered the issue when I first test streamed uploads.