S3 attachments

@thraxil This is working well for me. I added a few more commits.

I removed lodash because s3upload.js isn't using it at all. I don't know why that tutorial said to include it. And anyways, underscore.js provides most of lodash's functionality and we already have that in our codebase.

I added this branch under the ccnmtl repo so we can both push commits here.