Update helpers.js

This adds an option to space the JSON when it's being output. By writing the new helper like this:

```
{{json user 4}}
```

the JSON output goes from a flat, un-parseable list....

![](http://content.screencast.com/users/matt.pardee/folders/Jing/media/e05af00f-d88b-4736-b5fd-8cc178ffb452/00000146.png)

to

![](http://content.screencast.com/users/matt.pardee/folders/Jing/media/e98f1edc-d86c-459d-9a68-d01ae0716b27/00000145.png)