Well, something went wrong and i accidentally published a wrong version. So i had to publish a new version with the test code removed.
The billing permission stayed.
I was thinking about a paid version for a while, but couldn't decide how to implement it, a separate app, a key app or in-app billing. Google recently updated their libraries and made it simpler for developers to implement in-app billing. So now i am trying to add in-app billing to remove the ads.