Merge remote-tracking branch 'origin/master'

Readme.md

@@ -33,6 +33,10 @@ Example usage:
            Successfully installed Flask Werkzeug Jinja2
            Cleaning up...
 
+You can also add it to upcoming builds of an existing application:
+
+    $ heroku config:add BUILDPACK_URL=git@github.com:heroku/heroku-buildpack-python.git
+
 The buildpack will detect your app as Python if it has the file `requirements.txt` in the root. It will detect your app as Python/Django if there is an additional `settings.py` in a project subdirectory.
 
 It will use virtualenv and pip to install your dependencies, vendoring a copy of the Python runtime into your slug.  The `bin/`, `include/` and `lib/` directories will be cached between builds to allow for faster pip install time.