Wrapper AdSystem works the same as Inline and fixed the example usage in the README

The example in the README doesn't work so I've updated this to use the correct node module and it sets it to a variable with the correct name to be used later on in the example.

I updated setting the AdSystem in the Wrapper to match the Inline code.  Without out this fix if the Wrapper AdSystem was supplied as `{name: 'test'}` it would add it to the AdSystem element as an attribute instead of the element value, E.g. `<AdSystem name="test"/>` instead of `<AdSystem>test</AdSystem>`.