Python: Add a "make install" command and clarify installation docs (#578)

Closes #576

python/README.md

@@ -1,12 +1,19 @@
 This directory contains the code for the Python `brotli` module,
 `bro.py` tool, and roundtrip tests.
 
+We provide a `Makefile` to simplify common development commands.
+
 ### Installation
 
-If you just want to install the module from source, execute the
-following from the root project directory:
+If you just want to install the latest release of the Python `brotli`
+module, we recommend installing from [PyPI][]:
 
-    $ python setup.py install
+    $ pip install brotli
+
+Alternatively, you may install directly from source by running the
+following command from this directory:
+
+    $ make install
 
 ### Development
 
@@ -15,7 +22,7 @@ consuming.  Instead, we recommend using the `setuptools`
 "[development mode][]" to make the module available while still being
 able to edit the source files.
 
-We provide a `Makefile` to simplify common commands:
+For convenience, you may run the following commands from this directory:
 
     $ make          # Deploy the module in "development mode"
    
@@ -37,6 +44,7 @@ Then, to format all files in the project, you can run:
 See the [YAPF usage][] documentation for more information.
 
 
+[PyPI]: https://pypi.org/project/Brotli/
 [development mode]: https://setuptools.readthedocs.io/en/latest/setuptools.html#development-mode
 [Google Python Style Guide]: https://google.github.io/styleguide/pyguide.html
 [YAPF]: https://github.com/google/yapf