Merge pull request #597 from Precogs-com/master

underscorize resource type name in links

Author: lgebhardt

lib/jsonapi/resource_serializer.rb

@@ -307,7 +307,7 @@ def foreign_key_types_and_values(source, relationship)
       if relationship.is_a?(JSONAPI::Relationship::ToMany)
         if relationship.polymorphic?
           source._model.public_send(relationship.name).pluck(:type, :id).map do |type, id|
-            [type.pluralize, IdValueFormatter.format(id)]
+            [type.underscore.pluralize, IdValueFormatter.format(id)]
           end
         else
           source.public_send(relationship.foreign_key).map do |value|