[MISC]: More careful consideration of different xarray options

[jthielen]

What is your issue?

Test expected results under different xarray options

In the spirit of improving the quality of our tests (xref #60), it would be nice to implement tests where different relevant xarray options are enabled (using set_options as a context manager). This would likely make it easier to catch issues like #96 .

Xarray options in issue reports

Not sure the best way to do this (bundle into xwrf.show_versions()? Add another copy-paste box to the issue template?), but it could help with debugging if we knew the state of xarray.get_options.