Error with 'luaimageembed' on Windows

[Max Chernoff]

Hi Akira,

> "ba" should be "ab".
> I tested that the example worked on windows by
> 
>       ltn12.sink.file(io.open(file_name, "ab"))

Thanks. I've sent the fix to the upstream listed on CTAN

   https://github.com/csachs/luaimageembed/pull/5
   
-- Max