Evaluate Cloudfiles write() method. Borked for chunked writes?

[spaetz]

TODO: XXX It seems that our cloudfiles.write() takes all existing
data and appends "write(data)" data to it, sending the full monty
over the wire everytime. This would of course absolutely kill
chunked writes with some O(1^{n) performance and bandwidth
usage. But we do need chunked writes if we want to keep memory consumption at a reasonable level (#419). EVALUATE!}

Not familiar with cloudfiles but afaik we can iterate using some send() method.