add Blinka to 'setup.py->install_requires'; add PyPI install to README

Author: sommersoft

README.rst

@@ -28,6 +28,31 @@ Please ensure all dependencies are available on the CircuitPython filesystem.
 This is easily achieved by downloading
 `the Adafruit library and driver bundle <https://github.com/adafruit/Adafruit_CircuitPython_Bundle>`_.
 
+Installing from PyPI
+--------------------
+   If the library is not planned for PyPI, remove the entire 'Installing from PyPI' section.
+On supported GNU/Linux systems like the Raspberry Pi, you can install the driver locally `from
+PyPI <https://pypi.org/project/adafruit-circuitpython-pca9685/>`_. To install for current user:
+
+.. code-block:: shell
+
+    pip3 install adafruit-circuitpython-pca9685
+
+To install system-wide (this may be required in some cases):
+
+.. code-block:: shell
+
+    sudo pip3 install adafruit-circuitpython-pca9685
+
+To install in a virtual environment in your current project:
+
+.. code-block:: shell
+
+    mkdir project-name && cd project-name
+    python3 -m venv .env
+    source .env/bin/activate
+    pip3 install adafruit-circuitpython-pca9685
+
 Usage Example
 =============
 
@@ -85,4 +110,4 @@ Now, once you have the virtual environment activated:
 
 This will output the documentation to ``docs/_build/html``. Open the index.html in your browser to
 view them. It will also (due to -W) error out on any warning like Travis will. This is a good way to
-locally verify it will pass.
+locally verify it will pass.

setup.py

@@ -34,7 +34,7 @@
     author='Radomir Dopieralski & Adafruit Industries',
     author_email='[email protected]',
 
-    install_requires=['adafruit-circuitpython-busdevice', 'adafruit-circuitpython-register'],
+    install_requires=['Adafruit-Blinka', 'adafruit-circuitpython-busdevice', 'adafruit-circuitpython-register'],
 
     # Choose your license
     license='MIT',