feat(controller): make Procfile mandatory

At the moment, all custom Dockerfile apps will not start because the
'start' command is not present in the container. Instead, we can
generically parse the Procfile for the process type and start that
instead. This makes two important changes:

1) All applications **must** specify a Procfile
2) All custom Dockerfile apps must have access to cat, grep, cut and sh

The justification for 1) is so that we have a known place to search for
runnable processes. 2) is because of the change from `start web` to parse
the Procfile for the process types.

fixes #668
chore(contrib/ec2): update AMIs for build 298.0.0

based on the updated list at
https://coreos.com/docs/running-coreos/cloud-providers/ec2/
chore(contrib): remove docker project

This was a proof-of-concept project that's unsupported and not
in use.
Merge pull request #835 from deis/update-amis

chore(contrib/ec2): update AMIs for build 298.0.0
Merge pull request #836 from deis/remove-docker-contrib

chore(contrib): remove docker project
fix(controller): rename destroy() to delete() and call its super()

To ensure that we destroy containers and fleet jobs when deleting an
app, do so in the Django model method delete(), not the REST API-ish
destroy() which was not connected to anything.
chore(controller): update to Django 1.6.4 bugfix release

Details at https://www.djangoproject.com/weblog/2014/apr/28/bugfix-releases-issued/
fix(docs): rename client/containers.rst to ps.rst

Sphinx has been logging this error since #813 was merged:
```console
docs matt$ make server
sphinx-build -b dirhtml -d _build/doctrees   . _build/dirhtml
...
/Users/matt/Projects/deis/docs/client/index.rst:12: WARNING: toctree contains reference to nonexisting document u'client/ps'
```

It appears we forgot to rename the source file from containers.rst
to ps.rst, and doing so fixes the docset.
docs(localdev): add "Test Your Changes" section to local dev docs

Fixes #781.
docs(ec2): remove reference to obsolete script
Merge pull request #842 from deis/add-interactive-dev-docs

docs(localdev): add "Test Your Changes" section to local dev docs
Merge pull request #841 from deis/fix-client-ps-docs

fix(docs): rename client/containers.rst to ps.rst
Merge pull request #840 from deis/django-1.6.4

chore(controller): update to Django 1.6.4 bugfix release
Merge pull request #839 from deis/app-fleet-delete

fix(controller): rename destroy() to delete() and call its super()
Merge pull request #844 from deis/ec2-readme-cleanup

docs(ec2): remove reference to obsolete script
Merge pull request #834 from deis/procfile-mandatory

feat(controller): make Procfile mandatory
feat(test): add integration tests

Adds a test/ directory with a Rakefile that defines
integration tests to fully exercise a Deis cluster.

Currently these are written in Ruby, as the goal here was
to get tests implemented quickly. The tests were written so
they can be easily ported later.