Let people choose their JSON serializer; JSON:API is not circular

Gemfile.lock

@@ -3,7 +3,6 @@ PATH
   specs:
     fast_jsonapi (1.0.17)
       activesupport (>= 4.2)
-      multi_json (~> 1.12)
 
 GEM
   remote: https://rubygems.org/
@@ -61,7 +60,6 @@ GEM
       nokogiri (>= 1.5.9)
     mini_portile2 (2.3.0)
     minitest (5.10.3)
-    multi_json (1.13.1)
     nokogiri (1.8.1)
       mini_portile2 (~> 2.3.0)
     oj (3.4.0)

fast_jsonapi.gemspec

@@ -21,7 +21,6 @@ Gem::Specification.new do |gem|
   gem.summary = "fast JSON API(jsonapi.org) serializer"
 
   gem.add_runtime_dependency(%q<activesupport>, [">= 4.2"])
-  gem.add_runtime_dependency(%q<multi_json>, ["~> 1.12"])
   gem.add_development_dependency(%q<activerecord>, [">= 4.2"])
   gem.add_development_dependency(%q<skylight>, ["~> 1.3"])
   gem.add_development_dependency(%q<rspec>, ["~> 3.5.0"])

lib/fast_jsonapi/object_serializer.rb

@@ -1,7 +1,6 @@
 require 'active_support/core_ext/object'
 require 'active_support/concern'
 require 'active_support/inflector'
-require 'multi_json'
 require 'fast_jsonapi/serialization_core'
 
 begin

lib/fast_jsonapi/serialization_core.rb

@@ -65,8 +65,9 @@ module FastJsonapi
         end
       end
 
+      # Override #to_json for alternative implementation
       def to_json(payload)
-        MultiJson.dump(payload) if payload.present?
+        JSON.fast_generate(payload) if payload.present?
       end
 
       # includes handler

spec/spec_helper.rb

@@ -1,6 +1,5 @@
 require 'fast_jsonapi'
 require 'rspec-benchmark'
-require 'multi_json'
 require 'byebug'
 require 'active_model_serializers'
 require 'oj'