Fix output encoding

[Ilya Nazarov]

Hello. There are problem with non-english documents. No output encoding provided in presentation output, and browser uses "latin", but should use "utf-8".

[Ilya Nazarov]

Encoding fix

[Ilya Nazarov]

Change last string in s5.py from:

        return req.hdf.render(template), 'text/html'

to:

        return req.hdf.render(template), 'text/html;charset=utf-8'

[Alec Thomas]

(In [2565]) Added patch from Ilya Nazarov, thanks! Fixes #1804.