Lcg/chef 12 attr

See https://gist.github.com/danielsdeleo/da9a8d9a91cc8c2781b0
@danielsdeleo when i go in through `force_default!['foo']['bar'] = 'baz'` how is `reset` getting called in order to invalidate the cached merged objects?  Reading this code I thought I had a bug where I was missing calling reset here, but the spec tests seem to 'check' for this behavior and they pass.