Ported to new task states

Ported to new task stats...

I tested this against taskcluster-queue running locally... Hence, the hacks in `test/helper.js`. Note, that these hacks should work fine when not testing against local queue too...
(So now running against a queue running on localhost is just a config issue).

I know you're not particularly familiar with the code, so the review is mostly a formality... See if there is something crazy wrong... Or do nothing and I'll deploy this and hope it doesn't break the world :)

**DO NOT MERGE** this yet... I still need to port taskcluster-treeherder integration... before we can deploy this.