Draft of attribute syntax API

@zuazo  Those are great examples.  Thanks.

Do you typically have cases where those would be ambiguous?  As written, your examples would be fine as long as you didn't also have:

```
node['network']['interfaces']['eth0']['addresses']['11']['22']['33']['44']['netmask'] # set by ohai
node['proftpd']['virtual_host']['ftp']['example']['com']['default_root']
node['myapp']['conf']['settings']['.yml']['dbname']
```
However, I think the "fallback" behavior could make key lookup slow in the case of a miss, which I'm not thrilled with.