Currently, we have to make a temporary file when doing e.g. put(stringio_instance, xxx) or similar.
Paramiko #71 includes a patch that should mean we no longer have to do this. If/when that merges, update to take advantage (and bump our requirements to match...)
Should apply to both put and get.
Use new Paramiko getfo() to remove disk bounce in get().
Apply #787 to put()
Changelog re #787