Removes calling internal method that will be made private

Removes calling protected method `getVariantData()` as per https://code.google.com/p/android/issues/detail?id=68731 and https://groups.google.com/forum/m/#!topic/adt-dev/Kl_4qE164Ys , the method will be made private therefore calling it will break the plugin in the near future. 

Now the plugin relies only on the `variant` object. 

Fixes #11