add install instructions to README, enable setup.py

Author: brentru

README.rst

@@ -27,9 +27,6 @@ This is easily achieved by downloading
 
 Installing from PyPI
 =====================
-.. note:: This library is not available on PyPI yet. Install documentation is included
-   as a standard element. Stay tuned for PyPI availability!
-
 On supported GNU/Linux systems like the Raspberry Pi, you can install the driver locally `from
 PyPI <https://pypi.org/project/adafruit-circuitpython-minimqtt/>`_. To install for current user: