ref(builder): compress archive into tarball

When we removed pigz from slugbuilder, it changed the format to a
tar file. Compressing it with gzip by supplying tar the -z option
reverts this behaviour.
feat(deisctl): check for required configuration on platform install
docs(*): set required platform config before install/start
Merge pull request #2245 from gabrtv/fix-deisctl-docs

docs(*): set required platform config before install/start
Merge pull request #2244 from gabrtv/deisctl-required-keys

feat(deisctl): check for required configuration on platform install
Merge pull request #2218 from bacongobbler/tarball

ref(builder): compress archive into tarball
chore(release): update version to v0.14.1
Merge pull request #2247 from mboersma/release-v0.14.1

chore(release): update version to v0.14.1
feat(installing): add digitalocean guide
ref(installing_deis): move deis management
ref(docs): remove "register admin user" docs

This document is superseded by the documentation in
using_deis/install-client and in using_deis/register-user.
ref(docs): add link to installing Deis