In this cache method, the template engine is always called. If you want to cache
this as well, use renderFullCached().
Example:
return $this->renderCache('myCache', 'plugin1/default.tpl', function(){
return array('items' => heavyDbQuery());
});
Note: The $data callable is only called if the cache needs to regenerate (when it has been
invalidated or empty, or the view file changed).
If the callable $data returns NULL, then this will return NULL, too.