merge `bittorrent-client` into this module

[feross]

When I started the WebTorrent project I thought there were going to need to be two separate client implementations (bittorrent-client and webtorrent-client) - one for bittorrent, and an entirely different one for the webtorrent stuff, because WebRTC is so different. The plan was to tie the two together in a higher-level module.

Fortunately, this was not necessary because of the awesome “browser” field support in browserify. By substituting just a few modules, we can make the same module (webtorrent) work in node AND the browser, with the same codebase!

With the next WebTorrent release, you can:

• require('webtorrent') to use bittorrent in a node app or script. Bonus: Soon, your app will also download/seed from web users (more peers = faster downloads)
• require('webtorrent') to use webtorrent in the browser
• Lastly, you can run npm install webtorrent -g to get a nice command line app with chromecast, airplay, vlc, etc. video streaming support. It installs a webtorrent command.

I hope this makes it easier to get started with WebTorrent and easier to contribute.

[feross]

This is done and released as webtorrent 0.8.0. See commit 9368650

[feross]

Since bittorrent-client is now deprecated, I'm going to migrate all issues to this repo. I don't know if this will trigger tons of email notifications for each new issue/comment - if so, I apologize in advance.