Updated setup.py, encoding error

[Jaime02]

Hi, I got a issue when installing the module in Windows 10. Changing a single line fixed it, I think.

[vercel]

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[paulmelnikow]

Hmm, this actually doesn't work in Python 2:

Traceback (most recent call last):
  File "setup.py", line 9, in <module>
    with open("README.md", encoding="utf8") as f:
TypeError: 'encoding' is an invalid keyword argument for this function