task: make changes requested in code review

The changes included with this commit are:

* migrate `pillar.example` to `metadata/service/client.yml` per reclass
* allow users to specify an override `download_url` for helm and kubectl
binaries
diff --git a/README.rst b/README.rst
index aeb10c0..76c8463 100644
--- a/README.rst
+++ b/README.rst
@@ -91,7 +91,8 @@
 Sample pillars
 ==============
 
-See the [pillar.example](pillar.example) for a documented example pillar file.
+See the [default reclass pillar configuration](metadata/service/client.yml) for 
+a documented example pillar file.
 
 Example Configurations
 ======================