Training update

@apcomplete We can review tomorrow.

* Added multibuildpack with both Ruby and Node build packs
* Fixed one (of many) links in the training app that are tough to deal with.
* Updated and the gaslight_training gem.

Ultimately I'm going to go through and delete the old views for the training app that are still in gaslight.co. They are duplicated in the gem and they are being overridden by the files in this repo.