* api/metric changes from jmacd:jmacd/batch_obs_2
* Add an SDK test
* Use a single collector method
* Two fixes
* Comments; embed AsyncRunner
* Comments
* Comment fix
* More comments
* Renaming for clarity
* Renaming for clarity (fix)
* Lint
Update license header to standard format for source files missed prior.
Add license header to new source files.
Add Makefile check to test all `*.go` and `*.sh` files have a copyright
notice (or comment about them being auto-generated) within the first few
lines.
* Update api for Must constructors, with SDK helpers
* Update for Must constructors, leaving TODOs about global errors
* Add tests
* Move Must methods into metric.Must
* Apply the feedback
* Remove interfaces
* Remove more interfaces
* Again...
* Remove a sentence about a dead inteface