Merge pull request #403 from y-yagi/fix-ruby-warnings

Fix ruby warning

Author: kaspth

lib/sass/rails/helpers.rb

@@ -3,6 +3,7 @@
 
 module Sprockets
   module SassFunctions
+    remove_method :asset_data_url if method_defined?(:asset_data_url)
     def asset_data_url(path)
       Sass::Script::String.new("url(" + sprockets_context.asset_data_uri(path.value) + ")")
     end