Include Python pushgateway in Pushing docs

Currently only shell, Java and Go are listed. Python supports pushgateways as well but requires users to go to the client library page to discover about it.

content/docs/instrumenting/pushing.md

@@ -13,14 +13,16 @@ time series from these components to an intermediary job which Prometheus can
 scrape. Combined with Prometheus's simple text-based exposition format, this
 makes it easy to instrument even shell scripts without a client library.
 
-For more information on using the Pushgateway and use from a Unix shell, see the project's
+ * For more information on using the Pushgateway and use from a Unix shell, see the project's
 [README.md](https://github.com/prometheus/pushgateway/blob/master/README.md).
 
-For use from Java see the
+ * For use from Java see the
 [PushGateway](http://prometheus.github.io/client_java/io/prometheus/client/exporter/PushGateway.html)
 class.
 
-For use from Go see the [Push](http://godoc.org/github.com/prometheus/client_golang/prometheus#Push) and [PushAdd](http://godoc.org/github.com/prometheus/client_golang/prometheus#PushAdd) functions.
+ * For use from Go see the [Push](http://godoc.org/github.com/prometheus/client_golang/prometheus#Push) and [PushAdd](http://godoc.org/github.com/prometheus/client_golang/prometheus#PushAdd) functions.
+
+ * For use from Python see [Exporting to a Pushgateway](https://github.com/prometheus/client_python#exporting-to-a-pushgateway).
 
 ## Java batch job example