Expose as a module

barkeep in two flavours:

cli:
```
$ ../node_modules/.bin/barkeep
Listening at http://localhost:9000
Added: /index.html to list of watched files
Added: /test.js to list of watched files
Added: /test.map to list of watched files
```

or api:
```js
var root = __dirname; // serve files from here
var sp = 9000;            // optional static port
var lp = 35729;           // optional livereload port

var server = barkeep(root).listen(sp, lp, onListen);

// optional callback
function onListen() {
  console.log('listening');
}
```