Concurrency Fix (#94)

* Fix concurrency flag

* bump version

Author: richmolj

lib/jsonapi_compliable/configuration.rb

@@ -19,6 +19,8 @@ def initialize
     def experimental_concurrency=(val)
       if val && !defined?(Concurrent::Promise)
         raise "You must add the concurrent-ruby gem to opt-in to experimental concurrency"
+      else
+        @experimental_concurrency = val
       end
     end
   end

lib/jsonapi_compliable/version.rb

@@ -1,3 +1,3 @@
 module JsonapiCompliable
-  VERSION = "0.11.18"
+  VERSION = "0.11.19"
 end