Documentation cleanup and linkage for validator

activemodel/README

@@ -193,3 +193,26 @@ functionality from the following modules:
 
   {Learn more}[link:classes/ActiveModel/Validations.html]
   
+* Make custom validators
+
+   class Person
+     include ActiveModel::Validations
+     validates_with HasNameValidator
+     attr_accessor :name
+   end
+   
+   class HasNameValidator < ActiveModel::Validator
+     def validate(record)
+      record.errors[:name] = "must exist" if record.name.blank?
+     end
+   end
+  
+   p = ValidatorPerson.new
+   p.valid?                  #=>  false
+   p.errors.full_messages    #=> ["Name must exist"]
+   p.name = "Bob"
+   p.valid?                  #=>  true
+
+  {Learn more}[link:classes/ActiveModel/Validator.html]
+  
+  
\ No newline at end of file

activemodel/lib/active_model/validator.rb

 module ActiveModel #:nodoc:
-  # A simple base class that can be used along with ActiveModel::Validations::ClassMethods.validates_with
+  # A simple base class that can be used along with 
+  # +ActiveModel::Validations::ClassMethods.validates_with+
   #
   #   class Person
   #     include ActiveModel::Validations
@@ -28,7 +29,7 @@ module ActiveModel #:nodoc:
   #   end
   #
   #   class MyValidator < ActiveModel::Validator
-  #     def validate
+  #     def validate(record)
   #       record # => The person instance being validated
   #       options # => Any non-standard options passed to validates_with
   #     end