First pass at DSL additions for chef-client audit mode

@mcquin @sersut 
As a side note I prefer to have the error message in the exception in case we want to raise the same error somewhere else. Not super applicable here but we can alternatively do:

```
# exceptions.rb
class NoAuditsProvided < RuntimeError
      def initialize
        super "You must provide a block with audits"
      end
    end
```