* 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
* drop gauge instrument
* Restore the benchmark and stress test for lastvalue aggregator, but remove monotonic last-value support
* Rename gauge->lastvalue and remove remaining uses of the word 'gauge'
Co-authored-by: Krzesimir Nowak <krzesimir@kinvolk.io>
* Initial skeleton
* Revert noop provider removal
* Checkpoint
* Checkpoint
* Implement Bound instrument and LabelSet
* Add test
* Add a benchmark
* Add a release test
* Document LabelSetDelegator
* Lint and comments
* Add a second Meter test; fix typo; add a panic
* Add a test for the builtin SDK
* Address feedback