zip_export view does not respect it's own settings

it's possible to configure the zip download doc action. 

![screen shot 2014-05-05 at 09 21 42](https://cloud.githubusercontent.com/assets/437933/2875761/27d28e74-d426-11e3-8bd8-d8f6fa62a29a.png)


But it's still possible to call the `zip_download` view on other content.