Add Databags Example

Adds example usage of data bags to the default recipe with the data bag items being rendered in the sample.html template:

* reads "ingredients" from data bag "yummy"
* renders the "yummy ingredients" in the template
* update Vagrantfile for testing
* update to chefspec 3.0.0.beta.3 for stubbing data bags
* add spec example for testing
* update CHANGELOG