add methods and route and view to create rss feeds filtered by tags

Hello,

I added some code to create multiple rss feeds based on tags. 

I created a new view and route. You pass tags in on the url. I filter the items returned by result_items with the tags. If an item has all the tags, it passes the filter. 

Is this something you're interested in? If so, I'd be interested in your feedback. My branch is not ready to be merged, I only created the pull request to start a conversation.

Mike