Suggestion to provide cookbook with data instead of depending on chef-vault

**TL;DR: Allow definition of content that's otherwise downloaded using chef-vault.**

This is a suggestion to resolve [COOK-4677](https://tickets.opscode.com/browse/COOK-4677) (*"Shouldn't have to depend on using chef-vault"*).

We have a very simple approach to the problem: allow the user of *chef-vault* to decide whether to rely on chef-vault or not. This is done by having 2 attributes for the content normally downloaded by chef-vault. 

All feedback is much welcome. There's probably other ways of resolving the issue, but this worked for us at least.