docs(CHANGELOG): update for v0.12.0
chore(release): update version to v0.12.0
feat(contrib/digitalocean): Use native CoreOS integration

Use the native CoreOS experience as recently added by DigitalOcean.

This rewrites the previous provisioning script and replaced the tugboat
dependency by the new docl tool dependency.
Docl was written specifically to support the operations we need.
Once a new DigitalOcean CLI comes out with support for the metadata
flag the use of Docl can be reexamined.
feat(userdata): add deisctl to the coreos install
Merge pull request #1903 from Xe/feat/userdata/deisctl-in-userdata

feat(userdata): add deisctl to the coreos install
chore(deis): bump version to 0.13.0-dev
Merge pull request #1908 from bacongobbler/bump-version

chore(deis): bump version to 0.13.0-dev
Merge pull request #1776 from nathansamson/realcoreosdo

Use Real CoreOS on DigitalOcean
chore(*): remove deis-builder-data
refactor(controller): chaos scheduler tests and cleanup
Merge pull request #1917 from carmstrong/remove_builder_data

chore(*): remove deis-builder-data
Merge pull request #1913 from gabrtv/chaos

Chaos test framework with improved error handling
fix(*): Announce the published port to etcd

Announce the external instead of the internal port to etcd. Currently
all components are using the same internal and external port, so this
never broke deis.
Before publishing etcd, scan whether the internal port is opened
Builder listens on 22 (internal) and is published on 2223
chore(*): Rename PUBLISH to EXTERNAL_PORT

This makes the boot logic more understandable. This commit also fixes
some wrong comments, about what is published and what is checked.
chore(cache): Remove moved systemd unit file
Merge pull request #1864 from johanneswuerbach/announce-correct-port

fix(*): Announce the published port to etcd