spec and readme for airdrop/all_interfaces

As a novice to Boxen, Puppet, Ruby, TDD, and git, just want to make sure I'm on the right path here.

I figure the readme will have to be reorganized in the context of this refactor, so I'm just kinda putting the new content at the bottom. I imagine once the content's in there it won't be a big deal to move around later.

I'm also making sure `script/specs` runs with the specs I'm writing.

I'll just add to this PR as I go, but if I'm doing anything egregious, please let me know.