Mention pushing step and Kubernetes workaround

Updates:

- On Kubernetes you can avoid pushing your image by using a
different ImagePullPolicy.
- Verbiage on "single-node Docker cluster" now says Swarm cluster
for clarity due to user comment on Twitter.

Signed-off-by: Alex Ellis (VMware) <alexellis2@gmail.com>

Author: alexellis

docs/tutorials/CLI-with-node.md

@@ -149,7 +149,9 @@ Image: callme built.
 
 ### Push your function
 
-> If you are using a single-node Docker cluster on your laptop then you can skip this step.
+It is recommended to change the "tag" in the image field after each change, but by default OpenFaaS will attempt to pull your function from the Docker Hub or a remote container registry. This enables you to iterate on your functions quickly without changing their Docker "tag".
+
+> If you are using a single-node Docker Swarm cluster on your laptop then you can skip this step. If you are using `minikube` or a single-node Kubernetes cluster then you can set the ImagePullPolicy to "IfNotPresent" in the helm chart for the Kubernetes controller, this will allow you to work with images within your library.
 
 Now edit the `callme.yml` YAML file and set the "image" line to your username on the Docker Hub such as: `alexellis/callme`. Then build the function again.
 

docs/tutorials/first-python-function.md

@@ -119,7 +119,7 @@ hello-python        latest       e0344b26305f     one minute ago
 
 **Testing on a single host**
 
-If you're trying thing out on a single host, then you don't need to push your images to a registry, they'll just be used from the local Docker library.
+If you're trying this out on a single Docker Swarm cluster, then you don't need to push your images to a registry, they'll just be used from the local Docker library. If you're using Kubernetes and `minikube` and don't want to push to a remote container registry, then see the helm chart for how to set the `ImagePullPolicy`. This will enable use of images from the local library on Kubernetes.
 
 **Remote host, or multi-node cluster**