Updated spec to add a new configuration option 
'support_display_ads' to support  display  ads 
as described here:

https://support.google.com/analytics/answer/2444872?hl=en&utm_id=ad
Added the 'support_display_ads' configuration to
the renderer spec
Added a new configuration option 
'support_display_ads' to support  display  ads
Updated the render method to pick another snippet
depending on 'support_display_ads' configuration
Merge pull request #4 from sebastiandeutsch/master

support_display_ads configuration option