Upgrade multer dependency so we can leverage streams

[rglover]

Noticed that uploads can be slow and after digging found out that the latest version of Multer switched to using streams for uploads. Just need to refactor the uploads API and make sure we keep the shape of the returned data consistent (e.g., req.file or req.files still exists).

Another option is to just use Busboy directly (the core dependency Multer uses to parse uploads). Technically we don't need a bunch of fancy features—we just want the file data.

[rglover]

Just did a test. Only "gotcha" is making sure we handle the write to disk from the stream for local uploads and then pass the stream off to S3 for uploads there: https://stackoverflow.com/questions/37336050/pipe-a-stream-to-s3-upload.

[rglover]

Got it. See examples in your /cheatcode/experiments/multer2 directory.