Increase default :max_concurrency

lib/docs/core/requester.rb

@@ -14,7 +14,7 @@ module Docs
 
     def initialize(options = {})
       @request_options = options.extract!(:request_options)[:request_options].try(:dup) || {}
-      options[:max_concurrency] ||= 5
+      options[:max_concurrency] ||= 20
       super
     end