fix(controller): check image for hostname

Older images may still have a hostname in the database. Checking if
it has a hostname in the image name ensures backwards compatibility.
docs(dockerfiles): only allow one port exposed

This is due to https://github.com/deis/deis/issues/1156.
chore(controller): update PyYAML to 3.11

http://pyyaml.org/wiki/PyYAML#History
docs(gce): instructions for running Deis in Google Compute Engine

Adding instructions and script for running on Google Compute Engine. This changes existing CoreOS user-data to set permissions as strings instead of integers. PyYAML interperets integers preceded by 0 to be octal. 0755 would become 493 when converted.

closes #1036
fix(controller): set celery log level from envvar
Merge pull request #1584 from bacongobbler/dockerfile-docs

docs(dockerfiles): only allow one port exposed
Merge pull request #1588 from mboersma/update-pyyaml

chore(controller): update PyYAML to 3.11
chore(client): update docopt to 0.6.2

Minor changes:
https://github.com/docopt/docopt/compare/0.6.1...0.6.2
Merge pull request #1577 from deis/celery-debug

fix(controller): set celery log level to DEBUG
Merge pull request #1590 from mboersma/update-docopt

chore(client): update docopt to 0.6.2
chore(client): update requests to 2.3.0

https://github.com/kennethreitz/requests/releases/tag/v2.3.0
feat(controller): expose app url

While users should not have access to view a cluster's private
information like the cluster's auth key or the list of machines,
we need the cluster domain in order to expose the app url to the
user.
chore(builder): bump cedarish image
Merge pull request #1495 from andyshinn/google_compute_engine_tutorial

docs(gce): Instructions for running Deis in Google Compute Engine
chore(contrib/gce): make GCE script pass flake8

Also do a few stylistic changes:

 - prefer double quotes instead of single quotes
 - functionize commonly done tasks
 - use exit code
Merge pull request #1589 from mboersma/update-requests

chore(client): update requests to 2.3.0
Merge pull request #1538 from deis/check-hostname

fix(controller): check image for hostname
docs(installing_deis): clarify no web UI
docs(contributing/localdev): update localdev docs

[skip ci]
docs(reference): add `deis pull` reference