Prepare v0.9.3 - Githubissues

[x] This PR addresses an already opened issue (for bug fixes / features)
- This PR fixes issue #250
[x] Tests for the changes have been added (for bug fixes / features)
[x] Documentation has been added / updated (for bug fixes / features)
[x] HISTORY.rst has been updated (with summary of main changes)
[x] I have added my relevant user information to AUTHORS.md
What kind of change does this PR introduce?:
- Prepares a release that fixes an error that was introduced by myself when fixing an error that was introduced by the newest Xarray.
Does this PR introduce a breaking change?:

No, all changes are backwards-compatible.

roocs / clisops