doc(README.md): filling out the development section

Author: Aaron Schlesinger

README.md

@@ -22,49 +22,38 @@ The Deis project welcomes contributions from all developers. The high level proc
 - If your PR fixes any [issues][issues], make sure you write Fixes #1234 in your PR description (where #1234 is the number of the issue you're closing)
 - The Deis core contributors will review your code. After each of them sign off on your code, they'll label your PR with LGTM1 and LGTM2 (respectively). Once that happens, you may merge.
 
+## Prerequisites
 
-## Deploying
+In order to develop and test this component in a Deis cluster, you'll need the following:
 
-To build a dev release of this image, you will also need your own registry, but DockerHub or
-[Quay](https://quay.io/) will do fine here. To build, run:
+* [GNU Make](https://www.gnu.org/software/make/)
+* [Docker](https://www.docker.com/) installed, configured and running
+* A working Kubernetes cluster and `kubectl` installed and configured to talk to the cluster
+	* If you don't have this setup, please see [the installation instructions][install-k8s]
 
-```bash
-$ export DEIS_REGISTRY=myregistry.com:5000
-$ make docker-build docker-push
-```
-
-This will compile the Docker image and push it to your registry.
+## Testing Your Code
 
-After that, run
-
-```
-$ make deploy
-```
+Once you have all the aforementioned prerequisites, you can build and (optionally) push a new Docker image with your changes.
 
-Which will deploy the component to kubernetes. After a while, you should see one pod up with one
-running:
+This project has a [Makefile](https://github.com/deis/postgres/blob/master/Makefile) that makes these tasks significantly easier. It requires the following environment variables to be set:
 
-```
-NAME                  READY     STATUS    RESTARTS   AGE
-postgres-6wy8o        1/1       Running   0          32s
-```
+* `DEIS_REGISTRY` - A Docker registry that you have push access to and your Kubernetes cluster can pull from
+  * If this is [Docker Hub](https://hub.docker.com/), leave this variable empty
+  * Otherwise, ensure it has a trailing `/`. For example, if you're using [Quay.io](https://quay.io), use `quay.io/`
+* `IMAGE_PREFIX` - The organization in the Docker repository. This defaults to `deis`, but if you don't have access to that organization, set this to one you have push access to.
+* `SHORT_NAME` (optional) - The name of the image. This defaults to `controller`
+* `VERSION` (optional) - The tag of the Docker image. This defaults to the current Git SHA (the output of `git rev-parse --short HEAD`)
 
-You can then query this pod as you would with any other Kubernetes pod:
+Assuming you have these variables set correctly, run `make docker-build` to build the new image, and `make docker-push` to push it. Here is an example command that would push to `quay.io/arschles/postgres:devel`:
 
-```
-$ kubectl logs -f postgres-6wy8o
-$ kubectl exec -it postgres-6wy8o psql
-```
-
-
-## Testing
-
-You can run the test suite with
-
-```
-$ make test
+```console
+export DEIS_REGISTRY=quay.io/
+export IMAGE_PREFIX=arschles
+export VERSION=devel
+make docker-build docker-push
 ```
 
+Note that you'll have to push your image to a Docker repository (`make docker-push`) in order for your Kubernetes cluster to pull the image. This is important for testing in your cluster.
 
 ## License
 
@@ -82,3 +71,5 @@ limitations under the License.
 
 [prs]: https://github.com/deis/postgres/pulls
 [issues]: https://github.com/deis/postgres/issues
+[install-k8s]: http://kubernetes.io/gettingstarted/
+