Release notes

0.10.0 isn't out but I thought it'd be a good idea to have the release notes ready. People can update them as they add new stuff and when release time comes, gathering release notes is already done.

I've gone through the commits since 0.9.12 and I've added everything that looked like a feature to the release notes. I might have missed something though.

There are no release notes for 0.9.12. Maybe it'd be nice to have some even if the release was 2 days after 0.9.11 :)