Deal with jsonapi-serializable no longer calling to_json (#26)

* Fixes issue with jsonapi-serializable no longer calling to_json

* Pin jsonapi-serializable to >= 0.1.3

Author: Markus Mühlberger

jsonapi-rails.gemspec

@@ -14,7 +14,7 @@ Gem::Specification.new do |spec|
   spec.files         = Dir['README.md', 'lib/**/*']
   spec.require_path  = 'lib'
 
-  spec.add_dependency 'jsonapi-rb', '~> 0.1'
+  spec.add_dependency 'jsonapi-rb', '~> 0.1', '>= 0.1.3'
 
   spec.add_development_dependency 'rails', '~> 5.0'
   spec.add_development_dependency 'sqlite3'

lib/jsonapi/rails/renderer.rb

@@ -32,7 +32,7 @@ def rails_renderer(renderer)
         # has access to the request object.
         reverse_mapping = request.env[ActionController::REVERSE_MAPPING_KEY]
         options = options.merge(_reverse_mapping: reverse_mapping)
-        json = renderer.render(json, options) unless json.is_a?(String)
+        json = renderer.render(json, options).to_json unless json.is_a?(String)
         self.content_type ||= Mime[:jsonapi]
         self.response_body = json
       end