Remove `wrtc` dependency

[feross]

Currently, bittorrent-tracker, and thus WebTorrent, depend on the wrtc npm module.

wrtc doesn't build on some linux and windows systems. There are only prebuilt binaries for some platforms. On the other platforms, wrtc tries to build the module from source. This can take a long time and will always fail on systems that aren't set up with a compiler. It doesn't work at all on Windows. And, even though it's an optionalDependency it often breaks the whole install.

The truth is that wrtc is not a hard dependency for WebTorrent - only if you want WebRTC support to talk to web peers from node. Without wrtc, WebTorrent would just be a normal torrent client in node. If there aren't prebuilt wrtc binaries for a user's platform, I'd rather have it fail immediately (as an optionalDependency) without attempting a build from source. This would keep the install fast, and WebTorrent would continue to work just fine for end users (even though they wouldn't be able to talk to web peers).

I'm still experimenting with the best way to get WebRTC support in node. Too many people are having problems with wrtc, so I think I'm going to remove that dependency soon.

The good news is that Electron (atom-shell) has built-in support for WebRTC, since it's just Chromium. So it's not that important that every user of the webtorrent node program has WebRTC support via wrtc. It's more important that install is fast and works for everyone.

[feross]

I've opened an issue on wrtc requesting a wrtc-prebuilt module with the behavior I described above: node-webrtc/node-webrtc#200

Hoping that they agree that this is worthwhile.

cc @maxogden, @mafintosh, @substack, @dominictarr

[feross]

Good news! As of v0.35.0, webtorrent no longer depends on wrtc, so installing should be easy and error-free again!

In node.js, webtorrent will no longer connect to WebRTC peers, just normal TCP/UDP peers. If you want to connect to all types of peers, including WebRTC peers, from node.js, you need to use the webtorrent-hybrid package.

npm install webtorrent-hybrid

webtorrent-hybrid has the same command line interface (CLI) and module API as webtorrent. Just require('webtorrent-hybrid') if you need support for WebRTC peers.