Added documentation of the new :prefix option.

Signed-off-by: Michael Koziarski <michael@koziarski.com>

activesupport/lib/active_support/core_ext/module/delegation.rb

@@ -47,6 +47,31 @@ class Module
   #   Foo.new.min # => 4
   #   Foo.new.max # => 11
   #
+  # Delegates can optionally be prefixed using the <tt>:prefix</tt> option. If the value
+  # is <tt>true</tt>, the delegate methods are prefixed with the name of the object being
+  # delegated to.
+  #
+  #   Person = Struct.new(:name, :address)
+  #
+  #   class Invoice < Struct.new(:client)
+  #     delegate :name, :address, :to => :client, :prefix => true
+  #   end
+  #
+  #   john_doe = Person.new("John Doe", "Vimmersvej 13")
+  #   invoice = Invoice.new(john_doe)
+  #   invoice.client_name    # => "John Doe"
+  #   invoice.client_address # => "Vimmersvej 13"
+  #
+  # It is also possible to supply a custom prefix.
+  #
+  #   class Invoice < Struct.new(:client)
+  #     delegate :name, :address, :to => :client, :prefix => :customer
+  #   end
+  #
+  #   invoice = Invoice.new(john_doe)
+  #   invoice.customer_name    # => "John Doe"
+  #   invoice.customer_address # => "Vimmersvej 13"
+  #
   def delegate(*methods)
     options = methods.pop
     unless options.is_a?(Hash) && to = options[:to]