excluded_traders does not handle non-standard characters

[ikelso]

If you try to use russian characters in excluded_traders.txt you receive the following error:

Traceback (most recent call last):
File "cli.py", line 83, in
excluded_traders = [x.strip() for x in f.readlines()]
File "c:\users\byrdc\appdata\local\programs\python\python37\lib\encodings\cp1252.py", line 23, in decode
return codecs.charmap_decode(input,self.errors,decoding_table)[0]
UnicodeDecodeError: 'charmap' codec can't decode byte 0x9d in position 159: character maps to

I assume this would happen with any non-standard unicode character such as korean characters as well.

[maximumstock]

Great catch! I've merged your PR.