WIP: Add Miracle Grue Configurator

While wanting to add support for rafts, I saw that we could easily just generate the config for Miracle Grue on the fly with values passed in. This is still a WIP. I'd like to see any settings easily adjustable by just including them in the POST data.

* [x] Tests for MiracleGrueConfigurator
* [x] Support any configuration data being POSTed in
* [x] Update README
* [x] Update Hubot script