Replace respond_to?(:each) with respond_to?(:to_ary) for collection check. (#12)

Author: beauby

lib/jsonapi/renderer/document.rb

@@ -38,7 +38,7 @@ def data_hash
         primary, included =
           ResourcesProcessor.new(Array(@data), @include, @fields).process
         {}.tap do |hash|
-          hash[:data]     = @data.respond_to?(:each) ? primary : primary[0]
+          hash[:data]     = @data.respond_to?(:to_ary) ? primary : primary[0]
           hash[:included] = included if included.any?
         end
       end