Add encoding for open_file

[jxltom]

This is because open function will use system encoding which is got by locale.getpreferredencoding(False) according to python documentation. This may cause installation failure in non UTF-8 encoding systems.

At least, UnicodeDecodeError: 'gbk' codec can't decode byte 0x80 in position 2347: illegal multibyte sequence will be raised when setup in my system with encoding cp936.

[wanshun123]

I'm still getting this error (ERROR: Command errored out with exit status 1: python setup.py egg_info Check the logs for full command output.) when trying to install Kappa on Windows with pip install kappa