Add flickr.urls.getGroup and flickr.urls.getUserPhotos

I've been using the Flickr module for a while over on http://www.chasejarvisshoeproject.com and I'm using a couple URL method calls of the flickr API. I've been just re-adding my methods each time a new version comes out, but now that it's stable, I figured I'd submit a patch with the two methods I wrote.

Seems somewhere along the line the flickr.groups.pools.getPhotos call was added, that was the other I was using.

This is my first time submitting a patch, so if I've violated protocol somehow, be gentle with me and I'll be happy to do it right the next time.

If nothing else, this is here for me to use when a new version comes out.

Thanks!