Artifacts are now located in a central place.
This will enable us to downlaod artifacts when we need them (instead of
downloading them all upfront).
This also makes replacing sky_snapshot with gen_snapshot easier.
Also, make it clear the screen between results so it's more obvious
what's going on when you have new results (especially when you have
fixed everything).
* add google analytics
* send in the run target type
* track device type targets
* use the real GA code
* review comments
* rev to usage 2.0
* rev to 2.2.0 of usage; add tests
* review comments