docs(installing_deis): import AWS provisioning docs
docs(installing_deis): refer to contrib/ec2
docs(README): add badge pointing to latest docs
style(README): change two badges' colors to match Deis logo
fix(contrib/userdata): nse uses `docker exec`

Fixes shells into the container not having the correct envvars
docs(README.md): replace moved DNS link
docs(contrib): replace moved DNS links
docs(deisctl): reword comment
docs(contrib): refer to digitalocean guide
docs(installing_deis): import baremetal docs
docs(testing): add better instructions for contributors
ref(docs): error on warnings for all Makefile targets
docs(*): add Troubleshooting Deis docs
chore(release): update version to v0.15.1
chore(release): update version in master to v0.15.1+git
fix(tests): Allow TLS

Fixes https://github.com/deis/deis/issues/2230
docs(managing_deis): add MDS removal instructions
docs(*): specify required CoreOS version
fix(build.sh): fail on errors in Dockerfile two-tier builds

Without "set -e" at the top of each build.sh script, errors would
not propagate to the parent "docker build" process. In the case
of controller, this was masking a missing dependency which is now
fixed.
fix(registry): prefix "apt-get install" with "apt-get update"