CHANGELOG: Add metric changes to the changelog
### Added
- Added `operator-sdk up` command to help deploy an operator. Currently supports running an operator locally against an existing cluster e.g `operator-sdk up local --kubeconfig=<path-to-kubeconfig> --namespace=<operator-namespace>`. See `operator-sdk up -h` for help. [#219](https://github.com/operator-framework/operator-sdk/pull/219) [#274](https://github.com/operator-framework/operator-sdk/pull/274)
+- Added initial default metrics to be captured and exposed by Prometheus. [#323](https://github.com/operator-framework/operator-sdk/pull/323) exposes the metrics port and [#349](https://github.com/operator-framework/operator-sdk/pull/323) adds the initial default metrics.
### Changed
