[openspending-dev] Version 0.13.0

[Nick Stenning]

> ...and with that I'm going to introduce backwards incompatible changes
> in a minor version by introducing version 0.13.0 (oh isn't it wonderful
> how you can break rules as soon as you set them). 

For what it's worth, you're not breaking the rules by breaking backwards
compatibility in a 0.x.x version bump: see point 4 of
http://semver.org/.

-N