Add an example binding docker to localhost port

Add an example of binding the port to localhost to prevent external access
Add section header
fix(cluster-management): fix incorrect ordering instructions
fix(cluster-management): link to networkd ordering docs
feat(distributed-configuration): doc how to customize etcd unit
fix(installing-to-disk): Document new coreos-install channel option.

This replaces -V for selecting channel since it needs to be possible to
specify both a version and a channel.

Related: https://github.com/coreos/bugs/issues/29
Merge pull request #208 from marineam/channel

fix(installing-to-disk): Document new coreos-install channel option.
feat(running-coreos): minor GCE tweaks
Merge pull request #209 from robszumski/update-gce

feat(running-coreos): minor GCE tweaks
fix(GCE): tweak device path
Merge pull request #207 from robszumski/customize-etcd

feat(distributed-configuration): doc how to customize etcd unit
Merge pull request #202 from robszumski/networkd-correction

fix(cluster-management): fix incorrect ordering instructions
fix(sdk): Refresh doc on tagging/building releases.

Doesn't cover a number of things that are new but at least what it does
cover is no longer incorrect.
fix(*): Update image download URLs
fix(building-development-images): Update to reflect reality
fix(quickstart): clarity around example config
fix release doc
fix http urls
fix(quickstart): suggest using a cluster
Merge pull request #210 from marineam/buckets

Buckets of docs