add encrypted databag support

Updated old pull request to the newest head revision (https://github.com/DataDog/chef-datadog/pull/99)

Solves https://github.com/DataDog/chef-datadog/issues/96
This section mutates the default dd-agent kitchen tests with EDB (encrypted data_bag) support.  I think it may make more sense to have a second suite that tests for EDB, so we retain the default (no data_bag use), simple data_bag use, and then EDB use.

How does that sound?