Add a generated-image-url helper for rails31 specifically

lib/compass/app_integration/rails/actionpack31.rb

@@ -1,5 +1,5 @@
 # TODO figure something out so image_path works with rails integration
-%w(railtie).each do |lib|
+%w(railtie helpers).each do |lib|
   require "compass/app_integration/rails/actionpack31/#{lib}"
 end
 

lib/compass/app_integration/rails/actionpack31/helpers.rb

@@ -1,5 +1,5 @@
 module Sass::Script::Functions
-  def generated_image_url(path)
+  def generated_image_url(path, only_path = nil)
-    asset_url(path, "image")
+    asset_url(path, Sass::Script::String.new("image"))
   end
 end