docs(src/installing-deis/configuring-object-storage.md): clarify env var lookup order

also split up paragraph about BUCKET - hopefully that makes it more
readable

Author: Aaron Schlesinger

src/installing-deis/configuring-object-storage.md

@@ -29,7 +29,7 @@ The subsections herein explain how to configure these two inputs for each applic
 
 ### Environment Variables
 
-The builder looks for the below environment variables to determine where the object storage system is. The builder looks in-order for these variables. If it finds two, the one higher in the list will be used.
+The builder looks for the below environment variables to determine where the object storage system is.
 
 - `DEIS_OUTSIDE_STORAGE` - The external S3-compatible object storage system. Commonly used URLs:
   - `s3.amazonaws.com` for Amazon S3's `us-east-1a` region
@@ -38,7 +38,11 @@ The builder looks for the below environment variables to determine where the obj
   - They are set automatically by Kubernetes if you run [Minio](http://minio.io) as a service in the cluster
   - The [Helm chart for Deis](https://github.com/deis/charts/tree/master/deis-dev) installs Minio by default, so the Builder will use Minio by default.
 
-The builder also uses an environment variable to determine the name of the bucket it should store build artifacts in. It uses `git` by default, but if your credentials (see below) don't have read and write access to that bucket, you'll have to specify a different one. To do so, simply set the `BUCKET` environment variable to another value (`deis-builds`, for example).
+Note that if the builder finds a `DEIS_OUTSIDE_STORAGE_HOST` environment variable, it will ignore `DEIS_MINIO_SERVICE_HOST` and `DEIS_MINIO_SERVICE_PORT`. This behavior means that external object storage takes precedence over Minio.
+
+The builder also uses an environment variable to determine the name of the bucket it should store build artifacts in. It uses `git` by default, but if your credentials (see below for how credentials are configured) don't have read and write access to that bucket, you'll have to specify a different one. 
+
+To do so, simply set the `BUCKET` environment variable to another value (`deis-builds`, for example).
 
 ### Credentials