refactor ./lib/ws out into pull-ws-server

this also allows access to the http server, like this:

``` js
var scuttlebot = require('scuttlebot')
var server = scuttlebot(config)
server.on('request', function (req, res) {
  //handle http requests,
  //put a static server here, etc...
})
```

this means we can add a web ui as a scuttlebot plugin...