docs(components): explain a container's filesystem

This explains that a container's filesystem is ephemeral, and
that any changes made to disk will be wiped when the container
is either stopped or restarted.
Updated CHANGELOG.md.
Updated CLI binaries and links in client README.
Switch master to v0.8.0.
Merge pull request #715 from opdemand/filesystem-docs

docs(components): explain a container's filesystem
refactor(scheduler): use coreos/fleet for container scheduling

 - add concept of cluster for external job scheduling
 - first pass at new container api with mock scheduler
 - simplify build + config = release
 - deprecate configuration management and provider packages
 - deprecate node management features (formation/layer/node/provider/flavor)
refactor(scheduler): adapt web app to new cluster domain object
refactor(cm): remove deprecated cm and provider packages from test and coverage
refactor(client): changes for scheduler refactoring
refactor(builder): remove slug metadata from builder
feat(docker): deis meta project
refactor(scheduler): coreos scheduler implementation

Note an SSH wrapper is used to get around fleetctl ssh-agent requirement.  We will ultimately want to transition to an HTTP API for talking to fleet.  Until then, we should explore modifying fleetctl to remove the ssh-agent requirement for tunneling.

add cluster setup and teardown

announce to /deis/services/{container_name} with a sidekick container

 - add pull before start
 - add stop and remove in ExecStop
 - use hardcoded expose port 5000 for deis/slugrunner

parallelize scheduler tasks, add appropriate blocking

exclude scheduler from max-line-length

add sidekick container for logging, unit cleanup

add unit name regex, use it when templating units

add domain and options to SchedulerClient
fix destroy bug

update readme to reflect new scheduler workflow, with placeholders for not-yet-implemented features

first pass at systemd units for components

coreos contrib scripts, units and user-data helpers
refactor(builder): improve build + config = release

- add release version as header on build and config creation
- provide dynamic output on build/config CLI, including resulting release
- add `deis push` CLI shortcut for builds:create
chore(builder): upgrade to docker 0.9.1
feat(scheduler): add command handling for procfile-style execution
refactor(registry): new registry package with mock and private implementations

 - mock docker registry used for unit testing
 - private module used for adding layers to private registry
 - add registry.image field that includes build+config as a tagged image
 - added confd settings for a required private registry_url
refactor(deis-run): new `deis run` implementation and celery task
refactor(client): make apps_open cluster aware
chore(router): expose router on 80 and 443, add timeout for image download
chore(coverage): add .coveragerc in controller root