Read the README.rst with UTF8

[Lafudoci]

This change resolves the following decode issue on Windows CMD which uses CP950 by default.

C:\Users\Lafudoci>pip install monero-python
Collecting monero-python
  Using cached https://files.pythonhosted.org/packages/c6/71/71c89009a74a6ced66046fd65e668991b6e0cbf
fe41b16150dd102c7e5e3/monero-python-0.3.tar.gz
    Complete output from command python setup.py egg_info:
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "C:\Users\LeftC\AppData\Local\Temp\pip-install-a452m9hl\monero-python\setup.py", line 12,
 in <module>
        long_description = open('README.rst').read(),
    UnicodeDecodeError: 'cp950' codec can't decode byte 0xc5 in position 621: illegal multibyte sequ
ence

[emesik]

Thank you!