Update README

Update README inline with recent refactor done by @revett and @darnould ([v0.1.0](https://github.com/BBC-News/alephant-renderer/commit/8c9f7c3ae0f4efc59eb70e80a09a267df1f12bd7)).

![image.gif](http://cdn2.vox-cdn.com/uploads/chorus_asset/file/2443420/packnooo.0.0.gif)