Users can like dive sites

https://trello.com/c/cDSm4ctP/33-users-can-like-dive-sites

![likedivesites](https://cloud.githubusercontent.com/assets/8681076/5112943/8fc9ba24-6ff9-11e4-81d4-9419b6e5f7a5.gif)


Feels like this should be nested under the user, not the dive site. It's the user's like, not the dive site's. Thoughts?