Merge pull request #264 from vojtad/sprockets-3

Fixed TypeError: no implicit conversion of Sprockets::Asset into String

lib/compass-rails/patches/compass.rb

@@ -4,7 +4,7 @@
   def image_path_for_size(image_file)
     begin
       file = ::CompassRails.sprockets.find_asset(image_file)
-      return file
+      return (file.respond_to?(:pathname) ? file.pathname.to_s : file)
     rescue ::Sprockets::FileOutsidePaths
       return super(image_file)
     end