Merge pull request #705 from Krystosterone/master

supported_extensions attribute was added to the img tag when using image_tag

middleman-more/lib/middleman-more/extensions/automatic_image_sizes.rb

@@ -54,6 +54,8 @@ module Middleman
             end
           end
           
+          params = params.delete_if {|key| key == :supported_extensions }
+
           super(path, params)
         end
       end