Update CHANGELOG, improve message.

activesupport/CHANGELOG

 *Rails 3.2.0 (unreleased)*
 
+* Deprecated ActiveSupport::Memoizable in favor of Ruby memoization pattern [José Valim] 
+
 * Added Time#all_day/week/quarter/year as a way of generating ranges (example: Event.where(created_at: Time.now.all_week)) [DHH]
 
 * Added instance_accessor: false as an option to Class#cattr_accessor and friends [DHH]
 
-* Removed ActiveSupport::SecureRandom in favour of SecureRandom from the standard library [Jon Leighton]
+* Removed ActiveSupport::SecureRandom in favor of SecureRandom from the standard library [Jon Leighton]
 
 * ActiveSupport::OrderedHash now has different behavior for #each and
 #each_pair when given a block accepting its parameters with a splat. [Andrew Radev]

activesupport/lib/active_support/memoizable.rb

@@ -6,7 +6,7 @@ module ActiveSupport
   module Memoizable
     def self.extended(base)
       ActiveSupport::Deprecation.warn "ActiveSupport::Memoizable is deprecated and will be removed in future releases," \
-        "simply use Ruby instead.", caller
+        "simply use Ruby memoization pattern instead.", caller
       super
     end