add jspm package.json config

Further to #1655, I've included the necessary changes in the package.json here.

I've relaxed the jQuery constraint, so that this can be used with any version of jquery as simply as:

```javascript
  jspm.config({
    map: {
      jquery: 'jquery@1.8'
    }
  });
```

Being included before the require to `jspm.import('chosen')`

This allows the exact version to be environment-specific. Semver ranges will be supported in a future version as well, but that is a few months away.

The demo is still available here - http://jsbin.com/EfOYaBE/2/edit

Any further questions just ask.