Add custom date format to pages, add 'updated' field again

Reverts changes of c2a68cc where I accidentally removed support for 'updated' field, see comments of issue #164 for details.

plugins/date.rb

@@ -29,6 +29,16 @@ module Octopress
       end
     end
 
+    def format_date(date, format)
+      date = datetime(date)
+      if format.nil? || format.empty? || format == "ordinal"
+        date_formatted = ordinalize(date)
+      else
+        date_formatted = date.strftime(format)
+      end
+      date_formatted
+    end
+
   end
 end
 
@@ -38,32 +48,48 @@ module Jekyll
   class Post
     include Octopress::Date
 
-    attr_accessor :date_formatted
-
     # Convert this post into a Hash for use in Liquid templates.
     #
     # Returns <Hash>
     def to_liquid
-      format = self.site.config['date_format']
-      if format.nil? || format.empty? || format == "ordinal"
-        date_formatted = ordinalize(self.date)
-      else
-        date_formatted = self.date.strftime(format)
-      end
-
+      date_format = self.site.config['date_format']
       self.data.deep_merge({
-        "title"          => self.data["title"] || self.slug.split('-').select {|w| w.capitalize! || w }.join(' '),
-        "url"            => self.url,
-        "date"           => self.date,
+        "title"             => self.data['title'] || self.slug.split('-').select {|w| w.capitalize! || w }.join(' '),
+        "url"               => self.url,
+        "date"              => self.date,
         # Monkey patch
-        "date_formatted" => date_formatted,
-        "id"             => self.id,
-        "categories"     => self.categories,
-        "next"           => self.next,
-        "previous"       => self.previous,
-        "tags"           => self.tags,
-        "content"        => self.content })
+        "date_formatted"    => format_date(self.date, date_format),
+        "updated_formatted" => self.data.has_key?('updated') ? format_date(self.data['updated'], date_format) : nil,
+        "id"                => self.id,
+        "categories"        => self.categories,
+        "next"              => self.next,
+        "previous"          => self.previous,
+        "tags"              => self.tags,
+        "content"           => self.content })
     end
+  end
 
+  class Page
+    include Octopress::Date
+
+    # Initialize a new Page.
+    #
+    # site - The Site object.
+    # base - The String path to the source.
+    # dir  - The String path between the source and the file.
+    # name - The String filename of the file.
+    def initialize(site, base, dir, name)
+      @site = site
+      @base = base
+      @dir  = dir
+      @name = name
+
+      self.process(name)
+      self.read_yaml(File.join(base, dir), name)
+      # Monkey patch
+      date_format = self.site.config['date_format']
+      self.data['date_formatted']    = format_date(self.data['date'], date_format) if self.data.has_key?('date')
+      self.data['updated_formatted'] = format_date(self.data['updated'], date_format) if self.data.has_key?('updated')
+    end
   end
 end