RFC for Chef 12 Attr changes

The entirety of attributes were re-written, so I'm not sure there's code to point to.

Or did you mean some example chef code ala:

role data:
```
default_attributes 'foo' => { 'bar' => { 'bing' => {} }}
```
recipe:

```
node.default['foo'] = {'entire' => 'hash'}
```

In chef 10, `node['foo']` was now `{'entire' => 'hash'}` but in 11 it's a merge of those and there's no way to get the assignment you want.

I feel like the rest of this document outlines all the above in detail though, so I'm not clear waht you're asking me to add.