vagrant: add smoketests

These tests exercise all of the basic functionality of ZeroVM
application execution on ZeroCloud. This is useful to quickly test a dev
environment setup.
vagrant: pin devstack and keystone versions

This stuff changes and breaks the zerocloud environment too often. This
is an attempt at getting a stable environment for ZeroCloud and
application development.
vagrant: update README with smoketest instructions
Merge pull request #165 from larsbutler/smoketests

Smoketests for vagrant dev environment