Heads-up: Releasing 0.13.1

We're due to release 0.13.1 in a few days (or as soon as we clear the queue), 
as a bugfix release stabilising 0.13.0, allowing us to start on the 3 month release cycle for 0.14. 

Anything that isn't in 0.13.1 will have to wait until then to hit pypi.

Any objections, warnings or notes?

cc @jseabold , @yarikoptic, @juliantaylor, @takluyver
