Fix conflict between normalize and array_attribute macros.

Fix the `normalize` and `array_attribute` macros conflicting with each
other on the WikiPage model. This meant code like
`wiki_page.other_names = "foo bar"` didn't work. Both macros defined a
`other_names=` method, but one method overrode the other.

The fix is to use anonymous modules and prepend so we can chain method
calls with super.

app/logical/concerns/normalizable.rb

@@ -3,10 +3,14 @@ module Normalizable
 
   class_methods do
     def normalize(attribute, method_name)
-      define_method("#{attribute}=") do |value|
-        normalized_value = self.class.send(method_name, value)
-        super(normalized_value)
+      mod = Module.new do
+        define_method("#{attribute}=") do |value|
+          normalized_value = self.class.send(method_name, value)
+          super(normalized_value)
+        end
       end
+
+      prepend mod
     end
 
     private