routemaster-prometheus 1.3.13

Prometheus metrics reporting for Routemaster.

### routemaster-prometheus

Usage, in your Routemaster configuration file:

```yaml
plugins:
logging:
- class: routemaster_prometheus.logger:PrometheusLogger
kwargs:
path: /metrics
```

This package is based on the official Python Promeutheus bindings in
[`prometheus_client`](https://pypi.org/project/prometheus_client/). In order
for that package to operate in a multithreaded program such as Routemaster,
the environment variable `prometheus_multiproc_dir` must be set to a writeable
directory for temporary files. It does not need to be backed up as nothing
is persisted between application launches.

This is already done for you in the `thread/routemaster` Docker image
provided, but when deploying in a custom way you may wish to change this
directory.