Prepare 1.3.0 release

[davidperezgar]

Creating all changes necessary for releasing version 1.3.0.

[felixarntz]

Given the test failures in #784, we should resolve those first before proceeding with the next release.

Also, it may be nice to get #696 merged before the release, since we've been working on it for so long, and it seems more or less done now. I'll review both of these today.

[davidperezgar]

Yes, no problem. I was just preparing the release and wait for finishing that PRs.

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