add npm sandbox

Now you can:

- require node modules, boom!
- display controls or other ui in a `display` element

Issues:

- depends on `wzrd.in` - should we run a local browserify-cdn?
- bundles can take time to build, logging "bundle {start,end}" might not be enough
- https://github.com/maxogden/browser-module-sandbox/pull/7 should be merged
- i couldn't find a module / am too lazy atm, but having an example like this would be great:

```js
var sin = require('music-sin');
var pitch = require('music-pitch');

return function (t) {
  return sin(pitch('A0'));
};
```

Screenshot:

![screen shot 2014-08-09 at 5 59 07 pm](https://cloud.githubusercontent.com/assets/10247/3866660/1de7b480-1fde-11e4-851c-318be2dc72dc.png)