Add AEAD encryption (#23)

Author: jcmfernandes

lib/rack/session.rb

@@ -8,6 +8,5 @@ module Rack
   module Session
     autoload :Cookie, "rack/session/cookie"
     autoload :Pool, "rack/session/pool"
-    autoload :Memcache, "rack/session/memcache"
   end
 end