update buildstep to slugbuilder

Author: Matthew Fisher

docs/components/controller.rst

@@ -29,7 +29,7 @@ The controller stack includes:
 * PostgreSQL database as a backing store for Django
 * Celery / RabbitMQ for dispatching tasks
 * A lightweight *gitreceive* hook for ``git push`` access control
-* Docker and Buildstep to process Heroku Buildpacks
+* Docker and Slugbuilder to process Heroku Buildpacks and Dockerfiles
 
 Follow the :ref:`Operations Guide <operations>` to setup your own private
 Deis controller.

docs/gettingstarted/concepts.rst

@@ -98,5 +98,4 @@ See Also
 .. _`Twelve Factor model`: http://12factor.net/build-release-run
 .. _`backing services`: http://12factor.net/backing-services
 .. _`environment variables`: http://12factor.net/config
-.. _`Buildstep`: https://github.com/opdemand/buildstep
 .. _`converges`: http://docs.opscode.com/essentials_nodes_chef_run.html