Example commands should be portable

[ryanj]

Found a few examples that could use an update. Examples should work given a stock Kubernetes cluster, and should not depend on oc or OpenShift:

• content/page/pods.md: examples use oc to fetch token. Use kubectl instead (or avoid tokens?)
• content/page/pods.md: replace export $OPENSHIFT_API w/ export $K8S_API
• content/page/pods.md: curl example assumes namespace == 'default'
• content/page/nodes.md: needs fresh example output (mentions minishift)
• content/page/services.md: Services page mentions iptables, but it's not easy to access (minikube ssh example)

See also: #41, #60, #26, #21
Related content page: #64