title: Bookshelf.js relation for loosely related data
body: <p>I have a hotel table, and an amenity table. The only way they are "related" is via location, using PostGIS for PostgreSQL. In SQL I use a query like this to find the 5 nearest amenities to a hotel:</p>
  
  <p><code>SELECT amenity.name, amenity.brand, ST_Distance_Sphere(hotel.geom, amenity.geom)
  FROM amenity, hotel
  WHERE slug='city-plaza'
  ORDER BY ST_Distance(hotel.geom, amenity.geom)
  LIMIT 5;</code></p>
  
  <p>Is there a way I could add a "nearestAmenities" field to the Hotel model using Bookshelf, which would be a collection of Amenity?</p>