fix(docs): silence header warnings and restore broken links

Author: mboersma

docs/installing_deis/provision-controller.rst

@@ -37,7 +37,7 @@ Please see `contrib/rackspace`_ for details on using Deis on
 Rackspace cloud.
 
 DigitalOcean
----------
+------------
 
 The `contrib/digitalocean` section of the Deis project includes shell
 scripts and documentation to make it easy to provision a multi-node
@@ -46,7 +46,7 @@ Deis cluster on DigitalOcean_.
 Please see `contrib/digitalocean`_ for details on using Deis on DigitalOcean.
 
 Google Compute Engine
-----------
+---------------------
 
 The `contrib/gce`_ folder of the Deis project includes a Python script and
 documentation to help get up and running with a multi-node Deis cluster on

docs/using_deis/deploy-application.rst

@@ -30,9 +30,9 @@ Select a Build Process
 ----------------------
 Deis supports three different ways of building applications:
 
- 1. `Heroku Buildpack`_
- 2. `Dockerfile`_
- 3. `Docker Image`_
+ 1. `Heroku Buildpacks`_
+ 2. `Dockerfiles`_
+ 3. `Docker Images`_
 
 Buildpacks
 ^^^^^^^^^^
@@ -56,4 +56,4 @@ image in development or in your CI pipeline as you are in production.
 .. _`twelve-factor methodology`: http://12factor.net/
 .. _`Heroku Buildpacks`: https://devcenter.heroku.com/articles/buildpacks
 .. _`Dockerfiles`: http://docs.docker.io/en/latest/use/builder/
-.. _`Docker Image`: http://docs.docker.io/introduction/understanding-docker/
+.. _`Docker Images`: http://docs.docker.io/introduction/understanding-docker/