Move full_url_path from HasPage to Page

so that page_route() is accessible via Layout

lib/gollum/views/has_page.rb

@@ -15,9 +15,5 @@ module Precious
     def id
       @page.sha
     end
-
-    def full_url_path
-      ::File.join(@base_url, escaped_url_path)
-    end
   end
 end

lib/gollum/views/page.rb

@@ -169,6 +169,10 @@ module Precious
         @navbar
       end
 
+      def full_url_path
+        page_route(@page.escaped_url_path)
+      end
+
       # Access to embedded metadata.
       #
       # Returns Hash.