prometheus: proceed to release 0.13.1

[adamchalmers]

Hi all! Just wondering if y'all can cut a new release, so that my projects which use this crate can move away from parking_lot v0.11 -- basically just a release to get ea68788 out. That way I'd no longer have both parking_lot 0.11 and 0.12 in my tree :)

[adamchalmers]

Friendly ping to @lucab who cut the last release -- any chance of getting a patch release out for this?

[lucab]

I had some recent troubles which pushed me offline for a bit, and in turn this slipped off my radar.
I hope to get the new version published in the next few days, I started the release train at #440.

[adamchalmers]

Thanks very much, I appreciate it and I hope your troubles ease up soon.