chore(controller): update djangorestframework to 2.3.13

https://github.com/tomchristie/django-rest-framework/compare/2.3.12...2.3.13
chore(controller): update celery to 3.1.11

http://docs.celeryproject.org/en/latest/changelog.html#version-3-1-11
chore(controller): update redis to 2.9.1

https://github.com/andymccurdy/redis-py/compare/2.8.0...2.9.1
refactor(controller): removed unused ssh.py and its dependencies

We weren't using paramiko or pycrypto any longer.
Merge pull request #943 from deis/python-updates

chore(controller): update celery, djangorestframework, redis
refactor(ci): rewrite test harness in Go

Usually rewriting to achieve the same functionality is a fool's errand,
but in this case:
- contributors to Deis need to know Go and Python, not Ruby as well
- two interns this summer will begin by expanding our test suite, and
  they are interested in Go