[WIP] Test-kitchen with berkshelf (and more)

This pull request:
* Installs bundler for gem dependency management
* Installs berkshelf for cookbook dependency management
* Installs chefspec for unit testing
* Installs test-kitchen and serverspec for integration testing
* Extracts G5's custom wrapper cookbooks to separate repositories
* Installs nodejs via cookbook instead of apt so that we can use the nodejs_npm LWRP to install ember-cli and bower
* Institutes a new build process to deploy to Vagrantcloud

In other words, the actual recipe implementation for provisioning a box has changed very little, but everything around that code has changed a *lot*.

Marked as WIP because we are still deploying the g5stack base box to my personal Vagrantcloud account. We'll be ready to merge once G5 has an organization Vagrantcloud account.