Use actually defined methods, since and ago

Author: aeroastro

README.adoc

@@ -1865,12 +1865,12 @@ Use an instance of `ActiveSupport::Duration` as a receiver to calculate relative
 [source,ruby]
 ----
 # bad - It's confusing to read
-created_at.after(1.minute)
-expiration_date.before(3.days)
+created_at.since(1.minute)
+expiration_date.ago(3.days)
 
 # good
-1.minute.after(created_at)
-3.days.before(expiration_date)
+1.minute.since(created_at)
+3.days.ago(expiration_date)
 ----
 
 == Bundler