fix(README): cleanup the README a bit

Improves the README a bit by using more specific and enabling language.
Merge pull request #24 from philips/fixup-minor-readme-nits

fix(README): cleanup the README a bit
feat(etcd): Write etcd systemd snippet
Merge pull request #25 from bcwaldon/etcd-env-file

Write environment file from coreos.etcd options
feat(write_files): Set default permissions to 0644

Fix #26
fix(write_files): Create directories with mode 0755

Fix #28
Merge pull request #29 from bcwaldon/permissions

Fix permissions-related bugs
refactor(*): Break apart packages
Merge pull request #31 from bcwaldon/refactor

Refactor package layout
fix(etcd): Place etcd.service drop-in in /run
Merge pull request #33 from bcwaldon/etcd-dropin-run

fix(etcd): Place etcd.service drop-in in /run
feat(etcd): Default etcd name to /etc/machine-id
feat(etcd): Fall back to hostname if no machine-id
fix(system): Use os.Hostname
Merge pull request #32 from bcwaldon/etcd-name

feat(etcd): Default etcd name to /etc/machine-id
fix(etcd): Transform DISCOVERY_URL to DISCOVERY
Merge pull request #34 from bcwaldon/disco-url

fix(etcd): Transform DISCOVERY_URL to DISCOVERY
refactor(docs): rearrange order and add full example