Fix TypeError in news rss listing.

This fixes the
```
__call__() takes at least 2 arguments (1 given)
```
exception in `news_rss_listing`.

This is a quick-and-dirty fix, tests for the rss listing are still missing, because in Plone 4.3 the `portal_syndication` is remove (see #102) and therefore the rss feed view does not work for 4.3 and we cannot test it :angry: 

Instancing a `ViewPageTemplateFile` in class scope and in method scope is not the same! There is some magic involved. I refactored the view to instance both templates in class definition scope.

@elioschmutz please take a look