WebTorrent: dependency hygiene

I want to go through the whole webtorrent dependency tree to:

• De-duplicate dependencies
• Ensure that we’re using the latest version
• Pruning dependencies that aren’t needed in modern JS environments (to reduce risk and increase install speed)

This issue is a placeholder to track this task.

[feross]

@guanzo Done. Released stream-to-blob-url@3.

[feross]

Not finished yet, and already some good results:

Before:

$ npm ls --depth=99 --production | wc -l
     267

$ npm run size
   98338

After:

$ npm ls --depth=99 --production | wc -l
     227

$ npm run size
   95467