Data upload fails about half of the time

[pudo]

Based on various pieces of user feedback, it appears that uploading files to the site fails about half of the time. This seems to be caused by some weird interaction of the file-like upload object presented by Flask and the boto set_contents_from_fileobj handler, but it needs further investigation.

I wonder if it makes sense for us to implement direct S3 upload now, instead of futzing with this any more. I'd hoped to do this later because it's a bit more complex and ties us to S3 for good.