Move metrics module: lib/metrics.js -> lib/metrics/api.js
Implement DummyMetricsResource
Add DummyMetricsResource to DummyApi
Be consistent in docs for DummyMetricsResource and MetricStore: use 'number' as the type for metric values
Fix MetricStore tests after adding DummyMetricsResource
Remove the old metrics handler parts of DummyApi
Don't use pending_calls_complete in MetricStore's tests (it no longer works at will be removed soon)
Fix docs after adding the new DummyMetricsResource
Docstring fixes for DummyMetricsResource
Merge branch 'develop' into feature/issue-116-move-dummyapi-metrics-handlers-over-to-new-resource-infrastructure

Conflicts:
	lib/dummy/api.js
	lib/interaction_machine.js
Merge branch 'feature/issue-116-move-dummyapi-metrics-handlers-over-to-new-resource-infrastructure' into develop