Meganuke

This changes the suite to run every test in a "sandbox" via a executor user in order to fix #1225.

A test will be run by `testrunner` and then instead of a `stop` function being called to ask the framework to shut down nicely, we exit the shell started for `testrunner` and `kill -9` everything that that user started.

Preface: none of the numbers posted here are official in any capacity; they are here only as a proof of concept that tests are able to start, be stopped, and bind to ports. These numbers should be considered suspect since this is a new hardware environment and no tuning has been done towards tuning to a preview or final run. These numbers are simply here to prove that tests can be reliably stopped now.

[This](https://gist.github.com/msmith-techempower/4c81cfb49dcc12977169) is a preview-style run done on the Peak hardware using a build of the `meganuke` branch from about a week ago. One can search for "port" and will see a few, but not many, errors trying to bind to a port. I added more checks before tests are run to ensure that the ports are available before failing.

[This](https://gist.github.com/msmith-techempower/1e4b7595bb10bcc9ab00) is an preview-style run done on the Peak hardware illustrating that every test that started successfully bound to the port to which it was trying to bind.
If you remember at this point, can I get a comment above this line along the lines of `mount_options addresses issue mitchellh/vagrant#4997`