readme
merge `bittorrent-client` into this module

When I started the WebTorrent project I thought there were going to
need to be two separate client implementations (bittorrent-client and
webtorrent-client) that would get tied 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!

So, from now on, you can just `require(‘webtorrent’)` in node or the
browser, and it will just work. You can also `npm install webtorrent`
if you want to use bittorrent in a node app or script. Lastly, you can
`npm install webtorrent -g` if you want to use webtorrent as a command
line app (it installs a `webtorrent` command).
add test/basic.js back
split up test scripts; add test-browser-local