Let users view the comment history of any user

Previously: users couldn't access comment history
Problem: reddit lets you do this, and it's helpful if you want to see if a user you like has made any comments of comparable quality
Solution: make ```users#show``` display a user's comment history
Oh, is `anchor` a special option to `polymorphic_path`? I don't think `anchor_item` is also an option, then. I think I misunderstood.

Does this work?