FBGraph::Post with type photo add album property to retrieve album 

When a user uploads photo to an album you can found a post with type 'photo' in user's feed. But there wasn't way to fetch album infos and photo. Now from a user's post you can easily retrieve album and photos.

I haven't created a new connection module because I think it's a property only of the post.

I've created another branch because I'm not sure that you want to merge  :-)

Thanks
Giacomo