async: update to 3.2.0

lib/docs/scrapers/async.rb

@@ -1,7 +1,7 @@
 module Docs
   class Async < UrlScraper
     self.type = 'async'
-    self.release = '3.0.1'
+    self.release = '3.2.0'
     self.base_url = 'https://caolan.github.io/async/v3/'
     self.root_path = 'docs.html'
     self.links = {