template expansion of `json` in chef-solo

Fixes #362

Before this gets merged in I either want to delete the test or change it so its using the same code as the provisioner.

could either add a ProcessMap method to the template module or add it in the provisioner.

This way is a little hacky, but I can't see it going horribly wrong. It's much easier than walking the entire json struct, replacing both keys and values.