message: Document prometheus metrics in changelog. Fixes
diff: @@ -4,6 +4,7 @@ Any changes, including backwards incompatible changes will be listed here
  ## 10.1.0 (17/02/2019)
  +- Added ability to export prometheus metrics by basic auth protected `/metrics` endpoint. To enable include `PROMETHEUS_USERNAME` and `PROMETHEUS_PASSWORD` as environment variables. Those environment variables are required to authenticate using [HTTP basic authentication](https://developer.mozilla.org/en-US/docs/Web/HTTP/Authentication)
  - Dropped bunyan as dependency. Replaced with pino, a faster and actively maintained logging library
  - Updated dependencies
  