Unable to download large files

[dshafik]

Currently it's not possible to download large files due to in-memory buffering. The download function should instead stream directly to disk.

[city41]

It seems unable to upload large files too. a 5.5 meg file ends up truncated. Possibly for similar/the same reasons

[city41]

I have a pr out for the upload fix: #23

The download fix is different but likely very similar.