fix(controller): set default release image

If you scale an application with `deis scale cmd=1` before an
application has been pushed, it should deploy deis/helloworld.
However, the initial release (v1) does not have a image set for
the release, only the build. Setting the default to deis/helloworld
fixes the "scale before deploy" problem.
fix(client): clear cookies on login, logout, register

We should be clearing all cookies, since we can only be logged into
a single user and cluster at the same time. This fixes the 403 Forbidden
when being logged in immediately after registering.
fix(contrib): check that coreos/user-data has a discovery_url set
fix(vagrant): disable vagrant cachier if present

Vagrant cachier trys to use vboxfs mounts if it is installed. Disable it if present.
fix(readthedocs): install CLI requirements explicitly

Readthedocs.org began failing to generate our Python code autodocs
recently. Purging the build environment (use https://readthedocs.org/wipe/deis/latest/)
did not help. Their logs indicate Sphinx is confused by a version of
the urllib3 library that happens to be installed in the system python.
This packaging error was fixed in urllib3 1.8.2, see https://pypi.python.org/pypi/urllib3.
This adds the client's requirements explicitly to the docs_requirements.txt
so that this broken version of urllib3 isn't used.

This is also fixed by requests 2.3.0, but pinning urllib3 seemed like
a safer fix.
feat(docker registry): add Vagrantfile for Docker registry

Adds a contrib/docker-registry directory with a Vagrantfile that
configures and starts a VM with the Docker registry service.
Merge pull request #1117 from deis/fix-readthedox

fix(readthedocs): install CLI requirements explicitly
feat(contrib) Spin up an ELB

Fixes #1139
Use TCP > HTTP
fix(controller): disable web UI

fixes #1144
fix(controller) disable django admin URL

If you accidentally create an object that requires an external library
such as the Release object, no docker image will be pushed to the registry,
which is unintentional. This disables the django admin URL such that you can't
shoot yourself in the :shoe:.
docs(pip install): add --upgrade to `pip install deis`

This flag is safe to use as a default, and would avoid the problem
reported on IRC where an existing deis client stays out-of-date if
you follow our instructions exactly.
Merge pull request #1151 from deis/pip-upgrade

docs(pip install): add --upgrade to `pip install deis`
Merge pull request #1147 from deis/1114-disable-web

fix(controller): disable web UI from django urls
Merge pull request #1110 from btrepp/cachierfix

fix(vagrant): disable vagrant cachier if present
chore(*): rely on etcdctl in deis/base

As of deis/base#4, etcdctl v0.4.2 includes the --no-sync option.
We no longer need to install an etcdctl branch just to get this
option.
fix(logger): turn off verbose untar'ing

untar'ing go's tarball dumps out a lot of unneeded lines. This
cleans up the build process a bit.
docs(*): refactor and reorganize

Reorganize the docs to make more sense for users.
Merge pull request #1172 from deis/docs_restructuring

docs(*): refactor and reorganize
docs(*): fix toctree