Account for different handling of symbol keys in Rails 4.0

[bf4]

Comparing as a JSON string vs. as the Hash that is convert to JSON
works around the different Hash representations.

This likely has to do with the introduction of
config.action_dispatch.perform_deep_munge in Rails 4.1
See Rails issue 13420

  1) Failure:
  ActiveModel::Serializer::Adapter::Json::HasManyTestTest#test_has_many_with_no_serializer
  [active_model_serializers/test/adapter/json/has_many_test.rb:36]:
  --- expected
  +++ actual
  @@ -1 +1 @@
  -{:id=>42, :tags=>[{"attributes"=>{"id"=>1, "name"=>"#hash_tag"}}]}
  +{:id=>42, :tags=>[{"attributes"=>{:id=>1, :name=>"#hash_tag"}}]}

  2) Failure:
  ActiveModel::Serializer::AssociationsTest#test_has_many_with_no_serializer
  [active_model_serializers/test/serializers/associations_test.rb:74]:
  --- expected
  +++ actual
  @@ -1 +1 @@
  -[{"attributes"=>{"name"=>"#hashtagged"}}]
  +[{"attributes"=>{:name=>"#hashtagged"}}]

[joaomdmoura]

Awesome! I was about to go and take a look at this when received the PR 😁 tks!