Correctly sort recommendations based on score

This is a breaking change, as methods such as `recommended_books` will
no longer be chainable with other ORM query methods.

Signed-off-by: David Celis <me@davidcel.is>

lib/recommendable/rater/recommender.rb

@@ -25,7 +25,7 @@ def recommended_for(klass, count = 10, offset = 0)
         ids = Recommendable.redis.zrevrange(recommended_set, offset, count - 1, :with_scores => true)
         ids = ids.select { |id, score| score > 0 }.map { |pair| pair.first }
 
-        Recommendable.query(klass, ids)
+        Recommendable.query(klass, ids).sort_by { |record| ids.index(record.id.to_s) }
       end
 
       # Removes an item from a user's set of recommendations