hack comix for windows use gbk as filename code

Comix is a python application to view comic. it use pygtk as GUI library, so technically, it can be used under windows. But unfortunately, it has code problem under windows. OK, 2 fix it, open src/filechooser.py:214.

gbkpath = paths\[0\].decode('utf-8').encode('gbk')
self.\_window.file\_handler.open\_file(gbkpath)

done.