#254 does not support non-ascii character sets

[Wilson Chan]

well, I am a Chinese, using Simplified Chinese
characters, thus my code comments are in Simplified
Chinese. after the built of my source code solution, I
check out the chm file, all Simplified Chinese are
in "????" format, which is very common for me, since I
see most of the western softwares only support english
(ASCII), lack of support for other character sets.

I was wondering whether NDoc could be possible to
improve a little bit so that it could support other
character sets than only ASCII characters?