Merge pull request #95 from hernanat/no-double-wrap

prevents double wrapping of `BatchLoader::GraphQL`

Author: exAspArk

lib/batch_loader/graphql.rb

@@ -47,8 +47,13 @@ def self.wrap_with_warning(batch_loader)
     end
 
     def self.wrap(batch_loader)
-      BatchLoader::GraphQL.new.tap do |graphql|
-        graphql.batch_loader = batch_loader
+      case batch_loader
+      when BatchLoader::GraphQL
+        batch_loader
+      else
+        BatchLoader::GraphQL.new.tap do |graphql|
+          graphql.batch_loader = batch_loader
+        end
       end
     end