Remove unused code

lib/fast_jsonapi/fieldset.rb

@@ -1,7 +0,0 @@
-module FastJsonapi
-  class Fieldset
-    def initialize(fields)
-      @fields = fields
-    end
-  end
-end

lib/fast_jsonapi/object_serializer.rb

@@ -7,7 +7,6 @@ require 'fast_jsonapi/attribute'
 require 'fast_jsonapi/relationship'
 require 'fast_jsonapi/link'
 require 'fast_jsonapi/serialization_core'
-require 'fast_jsonapi/fieldset'
 
 module FastJsonapi
   module ObjectSerializer
@@ -120,7 +119,6 @@ module FastJsonapi
         subclass.race_condition_ttl = race_condition_ttl
         subclass.data_links = data_links
         subclass.cached = cached
-        subclass.fieldset = fieldset.dup if fieldset.present?
       end
 
       def reflected_record_type

lib/fast_jsonapi/serialization_core.rb

@@ -21,8 +21,7 @@ module FastJsonapi
                       :cache_length,
                       :race_condition_ttl,
                       :cached,
-                      :data_links,
-                      :fieldset
+                      :data_links
       end
     end