v3: avoid N+1 query in builds endpoint

lib/travis/api/v3/queries/builds.rb

@@ -1,7 +1,12 @@
 module Travis::API::V3
   class Queries::Builds < Query
     def find(repository)
-      repository.builds
+      filter(repository.builds)
+    end
+
+    def filter(list)
+      # filtering by branch, type, etc would go here
+      list.includes(:commit).includes(branch: :last_build)
     end
   end
 end