Users can search dive sites

https://trello.com/c/BSCAV8cq/36-users-can-search-dive-sites

![searchdives](https://cloud.githubusercontent.com/assets/8681076/5304160/fa144730-7bbd-11e4-8f0b-f538b7109517.gif)

image_tag seems to do it automatically. You need to do asset_path manually here as you are writing the `img` tag yourself