feat(router): add optional TLS support
feat(router): enable spdy
docs(router): add SSL documentation
feat(router): add X-Forwarded-Proto
fix(controller): handle partial deletion of domains
docs: clarify tags_set usage

Mention that tags are passed to the scheduler.
Merge pull request #2194 from bacongobbler/ssl_router

feat(router): add optional controller SSL support
Merge pull request #2281 from gabrtv/fix-domain-remove

fix(controller): handle partial deletion of domains
chore(release): update version to v0.15.0
Merge pull request #2288 from mboersma/release-0.15.0

chore(release): update version to v0.15.0
chore(release): update version in master to v0.15.0+git
Merge pull request #2289 from mboersma/release-0.15.0+git

chore(release): update version in master to v0.15.0+git
Merge pull request #2283 from ngpestelos/clarify-tags-set

docs: clarify tags_set usage
feat(docs): add digitalocean guide
ref(docs): shift management docs, add provider-specific docs
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This document is superseded by the documentation in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
fix(docs): add internal links for installation guides
ref(docs): add installation docs for deisctl
ref(docs): move DNS hints into sidenotes